In short, Satan is the central embodiment of all evil. Satan is a Hebrew word meaning "adversary" (opposer, enemy) as "one to lie in wait"; hence, "the snares of the devil." Devil in Greek is Diabolos and means "accuser, slanderer."

Satan used to go by the Hebrew name Helel which was translated into the familiar Latin name Lucifer and means "Light Bearer" or "Shining One". He is also commonly known as the accuser of our brethren, evil one, deceiver, murderer, lawless one, father of all lies, tempter, prince of darkness, great dragon, serpent, snake, the beast, Beelzebul the prince of demons, spirit of falsehood, man of sin, son of perdition, prince of the air, the Antichrist etc.

The book of Genesis shows that God made mankind in His image:

"And God [ELoHIM] said, 'Let us make man [ADaM] in our image, according to our likeness. And they shall have dominion over the fish of the sea, and over the birds of the sky, and over the cattle and over all the earth, and over every creeping thing that creeps on the earth.' And God [ELoHIM] created man [the ADaM] in His own image, in the image of God [the ELoHIM] He created him; male and female He created them. And God [ELoHIM] blessed them. And God [ELoHIM] said to them, 'Be fruitful and multiply and fill the earth and subdue it. And have dominion over the fish of the sea, and over the birds of the sky, and over every living thing that moves on the earth.'" (Genesis 1:26-28)

This understanding of "the image of God" is supported by the immediate text, which shows that mankind's duties included having dominion over the earth and every living creature on it. This interpretation is also supported by a related passage of Scripture in Psalm 8:

"What is man that You are mindful of him, and the son of man [ADaM] that You visit him? For You have made him a little less than God [the ELoHIM], and You crown him with glory and splendor. You make him have dominion over the works of Your hands; all things You put under his feet, the sheep and the cattle, all of them, and even the beasts of the field, the birds of the sky, and the fish of the sea, everything that passes through the paths of the seas." (Psalm 8:4-8)

In addition to showing the position of mankind on the earth, this psalm also alludes to the reason for Satan's ultimate fall. Verse 5 tells us that humanity was made "a little lower than the Godhead". However, it was men, not angels, who were given rulership over the earth.

Lucifer was the Anointed Cherub. Anointed means to be set apart for God's divine purpose. It also means "bestowal of Gods divine favor", and "appointment to a special place or function."

Like man, the angels were created perfect, and with a free will.

God had given Lucifer power and authority. But Lucifer perverted that power and wanted to exalt himself above God rather than "just" be the Angel of God.

As Ezekiel 28:12 tells us, Satan was "the model of perfection, full of wisdom and perfect in beauty" when he was created. Yet neither he nor any of the other angels were given dominion over the earth initially. Rather, Adam, a being Satan must have considered inferior to himself, was given this power. It's easy to see why Satan's pride led him to sin.

Ezekiel 28 continues to give us information about Satan:

13 "Thou hast been in Eden the garden of God; every precious stone was thy covering, the sardius, topaz, and the diamond, the beryl, the onyx, and the jasper, the sapphire, the emerald, and the carbuncle, and gold: the workmanship of thy tabrets and of thy pipes was prepared in thee in the day that thou wast created.

14 Thou wast the anointed cherub that covereth; and I have set thee so: thou wast upon the holy mountain of God; thou hast walked up and down in the midst of the stones of fire [planets].

15 Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee.

16 By the multitude of thy traffic the midst of thee was filled with violence, and thou hast sinned: therefore have I cast thee as profane out of the mountain of God: and I have destroyed thee, O covering cherub, from the midst of the stones of fire [planets].

Note, the Hebrew word rendered "traffic" is rekulla. And rekulla is derived from the root word rakal, which means "to go about." A closely-related derivative, rakil, means "slanderer" which brings us to the meaning of the word "devil".

The word "covering" is from the Hebrew word "cakak", and means "to cover over, guard, protect, defend, hedge in, to entwine, to fence in".
It was Lucifer’s job to protect the very planets he corrupted. This was one of his duties that gave him so much pride.

17 Thine heart was lifted up because of thy beauty, thou hast corrupted thy wisdom by reason of thy brightness: I have cast thee to the ground, I have laid thee before kings, that they may behold thee.

18 By the multitude of thine iniquities, by the iniquity of thy traffic thou hast defiled thy sanctuaries; therefore have I brought forth a fire from the midst of thee, it shall devour thee, and I have turned thee to ashes upon the earth in the sight of all them that behold thee."

The account of Ezekiel 28 implies that Satan, likely through peddling his slander, turned one third of the angelic host against God (Rev. 12:3-4). It's not hard to imagine that Satan went around to the angels, seeking to build support for his contention that they were far better qualified to run the earth than mankind was.

Eventually, Satan developed a plan that he must have felt would deliver to him the position he believed should have rightfully been his in the beginning. He decided to deceive man in the Garden into disobeying God's direct command. After having proven mankind unworthy of the rulership position God had placed them in, Satan, in his arrogant pride, must have thought God would see that he should be given authority over the world in their place.

It's in this context that we see Satan approach Eve in the Garden of Eden in Genesis 3:

"Now the serpent was more cunning than any beast of the field which the LORD God [ELoHIM] had made. And he said to the woman, 'Is it true that God [ELoHIM] has said, "Ye shall not eat of every tree of the garden"?' And the woman said unto the serpent, 'We may eat the fruit of the trees of the garden; but of the fruit of the tree in the midst of the garden, God [ELoHIM] has said, "Ye shall not eat thereof, nor shall ye touch it, lest ye die".' Then the serpent said unto the woman, 'Die? You will not die. For God [ELoHIM] knows that in the day you eat of it, your eyes will be opened, and you will be like God [ELoHIM], knowing good and evil.' And the woman saw that the tree was good for food, that it was pleasant to the eyes, and that it was a tree desirable to make one wise. So she took of its fruit and ate, and she also gave unto her husband who was with her, and he ate." (Genesis 3:1-6)

The Hebrew word translated "serpent" in the above passage is nachash and means "to shine". The proper translation of hanachash in Genesis 3 would be "the Shining one". This understanding of nachash fits in very well with Paul's description of Satan appearing as an "angel of light":

"And it's no wonder, for Satan himself masquerades as an angel of light." (2 Corinthians 11:14)

Notice Satan's tactics with Eve. He didn't lie to her outright, but instead he twisted the truth. He led Eve to doubt God's word.

Although Satan apparently believed that the downfall of mankind would benefit him, it actually turned out to be his undoing. God was not pleased with his role in man's disobedience, and he was cursed for his deviousness:

"And the LORD God [ELoHIM] said unto the serpent: 'Because thou hast done this, thou art cursed above all cattle and above every beast of the field. Upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life. And I will put enmity between thee and the woman, and between thy seed and her seed; He shall bruise thy head, and thou shalt bruise His heel.'" (Genesis 3:14-15)

Satan's plan to rectify the "mistake" God had made by putting humans in charge of the earth backfired. The same applies to Satans attempt to show God the flaws of man, in which he revealed his own shortcomings. This resulted in God placing an age-lasting animosity between mankind and Lucifer. From that point forward, Lucifer "the Shining one" became haSatan "the Adversary" of humanity.

The enmity God placed between man and Satan is alluded to by Paul in the conclusion of his letter to the Romans:

"But the God of peace shall crush Satan under your feet quickly. The grace of our Lord Jesus Christ be with you." (Romans 16:20)

What is Satan's status?

In man's place, Satan became the temporary ruler of the world. The devil tempting Jesus in the wilderness clearly shows this:

"And the devil, taking Him up into a high mountain range, showed unto Him all the kingdoms of the inhabited world in a moment of time. And the devil [DIABOLOS] said unto Him, 'I shall give all this authority and their glory unto you, for it has been delivered to me, and I give it to whomever I wish. Therefore if you will bow and worship me before my eyes, all shall be yours.'" (Luke 4:5-6)

Satan tempted Jesus for the same reason he had enticed Eve in the Garden. He knew that Jesus was in the process of regaining rulership over the world and replacing him. He also knew that if he could get Jesus to sin (as he had with Adam and Eve), then he could thwart God's plan and remain the ruler of the world. 
Where Adam and Eve had succumbed to Satan's deception and disqualified mankind from ruling the earth, Jesus withstood the temptation and triumphed. This victory paved the way for him to eventually reclaim rulership at his second coming.

Just before his crucifixion, Jesus alluded to Satan's status as the current ruler of the world:

"I will no longer talk much with you, for the prince of this world is coming, and he has nothing in Me, whatsoever." (John 14:30)

Paul refers to Satan as "the god of this age" in his second letter to the Corinthians:

"But even if our gospel is veiled, it is veiled to those who are perishing, in whom the god of this age has blinded the minds of the unbelieving, so that the light of the glorious gospel of Christ, who is the image of God, should not shine upon them." (2 Corinthians 4:3-4)

The Bible clearly states that Satan is the prince and ruler of this world and age (John 12:31 & 14:30, Eph. 6:12, Luke 4:6-7, and 2 Cor. 4:4) and in fact has dominion over this fallen world.

How does Satan affect mankind?

Because Satan enticed mankind to sin and bring death upon themselves, he is called a murderer:

"The devil was a murderer of men from the beginning, and abode not in the truth, because there is no truth in him. Whenever he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it." (John 8:44)

Mark's Gospel also shows us that Satan is blinding men so they can't see the good news of the Messiah:

"The sower soweth the word. But the ones by the wayside are those where the word is sown:
Whenever they hear, Satan comes immediately and takes away the word that was sown inside of them." (Mark 4:14-15)

In the following passage Jesus is talking about Satan after healing a possessed man:

"But when the Pharisees heard this, they said, 'This man does not cast out demons, only by the means of Beelzebul, the prince of demons.' But Jesus knowing their thoughts, said to them, 'Every kingdom divided against itself will be laid waste, and every city or house divided against itself will not stand. So if Satan casts out Satan, he is divided against himself. How then will his kingdom stand?'" (Matthew 12:24)

Here Satan is called "Beelzebul," which literally means "lord of the flies." He is identified as the "prince of demons" who possesses people and causes them harm. And we also find that Satan is the ruler of the fallen angels and demons.

Below are more verses showing that Satan brings sickness and ailments upon people oppressing and binding them therewith:

"And behold, there was a woman who had a spirit of infirmity for eighteen years, and she was bent together in herself and was not able to straighten up all the way. But when Jesus beheld her, He called out to her and said to her, 'Woman, you are delivered from your infirmity.' And He laid hands upon her, and immediately after she was made straight, and glorified God." (Luke 13:11-13)
"But this woman, being a daughter of Abraham, whom Satan has bound, lo, eighteen years, ought she not to be loosed from this bond on this Sabbath day?" (Luke 13:16)

"How God anointed Jesus of Nazareth with the Holy Spirit and with power, who went about doing good and healing all those oppressed by the devil, for God was with Him." (Acts 10:38)

Contrary to popular opinion, the Bible clearly shows that Satan has not been restricted to hell after his fall. Indeed, the Old Testament shows that, before the first coming of Jesus the Messiah, Satan continued to have access to the very throne of God:

"Now there was a day when the sons of God [ELoHIM] came to present themselves before the LORD, and Satan also came into their midst." (Job 1:6)
"Again there was a day when the sons of God [ELoHIM] came to present themselves before the LORD, and Satan also came into their midst to present himself before the LORD." (Job 2:1)

Satan used his access to the heavenly throne to slander and accuse God's people before God as well as the divine council, as the story in Job shows. Zechariah also saw Satan in action as the accuser in a vision:

"And he showed me Joshua the high priest standing before the Angel of the LORD, and Satan standing at his right to accuse him. The LORD said unto Satan, 'The LORD will rebuke thee, Satan! Yea, the LORD that hath chosen Jerusalem, will rebuke thee! Is not this a brand plucked out of the fire?'" (Zechariah 3:1-2)

Was Satan cast out of heaven?

Yes, in the verse below, Jesus is associating a great light with the fall of Satan from heaven, as would be appropriate for a being whose other name means light bearer:

"I beheld Satan as lightning fall from heaven." (Luke 10:18)

Lucifer's fall from heaven is recorded in the Bible when he wanted to take God's place as Lord over all:

"Hell from beneath is moved for thee to meet thee at thy coming. It stirreth up the dead for thee, even all the chief ones of the earth; and from their thrones it raiseth up all the kings of the nations. All of them speak and say unto thee, 'thou art also faint as we art, thou art likened unto us. Thy grandness is brought down to the grave, with the noise of thy viols: Maggots are the bed beneath thee, and worms are thy covering." (Isaiah 14:9-11)

"How art thou fallen from the heavens, O Lucifer (Shining One), Helel Ben-Shachar (Son of the Dawn)! How art thou cut down to the ground, thou who striketh down the nations! For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God [ELoHIM]; and I will sit upon the mount of the congregation, in the sides of the north: I will ascend above the heights of the clouds; I will be like the Most High. Yet thou shalt be brought down to hell, to the sides of the pit." (Isaiah 14:12-15)

Jesus, just before his crucifixion, stated that his triumph on the cross would allow for Satan to be cast out of heaven:

"Now is the judgment of this world, now shall the prince of this world be cast out; and I, when I am lifted up from the earth, will draw all men unto Myself." (John 12:31)

"Concerning the judgment, because the prince of this world has been judged." (John 16:11)

"The Son of Man shall send forth his angels, and they shall gather out of his kingdom all manipulators and those who practice lawlessness, and shall cast them into the furnace of fire; there shall be the weeping and gnashing of teeth."
(Matthew 13:41-42)

"Then shall He say also unto them on the left hand, 'Depart from Me, ye cursed, into everlasting fire, prepared for the devil and his angels.'" (Matthew 25:41)

Christ told his disciples that when he had gone back into heaven after his resurrection, the Father would send His Spirit to teach them all things and bring them into remembrance of all the things that he had said to them (John 14:26). But in addition, he warned them of the coming of Satan to the earth after his departure.

"And then the lawless one will be revealed, whom the Lord Jesus shall overthrow with the spiritual breath of His mouth and destroy with the brightness of His presence. The presence of the lawless one is in accordance with the power of Satan displayed in all kinds of counterfeit miracles, signs and wonders, and in every sort of deceitful unrighteousness amongst those who will perish because they received not the love of the truth that they might be saved. And for this reason God shall send them a powerful delusion, that they believe the lie, so that all be damned who believed not the truth but had pleasure in unrighteousness." (2 Thessalonians 2:8-12)

"And the angels which kept not their first estate, but abandoned their own habitation, he hath kept in imperceptible bonds under darkness unto the judgment of the great day." (Jude 1:6)

When Christ triumphantly returned to heaven after his crucifixion and resurrection (Rev. 12:5), Satan and his angels were cast out and no longer had access to the throne:

"And there was war in heaven. Michael and his angels fought against the dragon; and the dragon fought and his angels, but prevailed not, neither was their place found in heaven any more. And the great dragon was cast out, that serpent of old, called [DIABOLOS] the Devil, and [SATANAS] Satan, who deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him." (Revelation 12:7-9)

Note that Satan is cast into the earth, not onto the earth.

John records an angel speaking from heaven who gives warning to the earth about Satan:

"And I heard a great voice saying in heaven, 'Now is come salvation, and power, and the kingdom of our God, and the authority of His Christ, for the accuser of our brethren was cast down, he, who accused them before the eyes of our God by day and by night. And they overcame him by the blood of the Lamb and by the word of their testimony, and they did not love their life even unto death. Therefore rejoice, ye heavens, and those who dwell therein! Woe to the inhabitants of the earth and the sea! For the devil has come down to you, being furious, because he knoweth that he hath but a short time.'" (Revelation 12:10-12)

"And the beast was captured, and with him the false prophet that wrought miracles before his eyes, with which he deceived them that had taken the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone." (Revelation 19:20)

Now let's look at the final destiny of Satan. What do the Scriptures say will be his ultimate fate? Revelation 19 describes the battle between the Christ and the forces of the Antichrist at the end of this age. After the defeat and destruction of the beast and the false prophet, the Bible reveals that Satan himself will be captured and imprisoned for a thousand years:

"And I saw an angel descending from heaven, having the key to the bottomless pit [Abyss] and a great chain in his hand. He laid hold on the dragon, that serpent of old, which is the Devil [DIABOLOS] and Satan [SATANAS], and bound him for a thousand years. Then he cast him into the bottomless pit [Abyss], and shut him up, and set a seal upon him, so that he should no longer deceive the nations until the thousand years will be fulfilled. But after this he must be released for a season." (Revelation 20:1-3)

"And it shall come to pass in that day, that the LORD shall visit the iniquity of the host of the high places on high, and the kings of the earth upon the earth. And they shall be gathered like prisoners are gathered in the pit, and shall be locked up in the dungeon; and after an abundance of days, shall their iniquity be visited." (Isaiah 24:21-22)

"And when the thousand years are expired, Satan shall be released from his prison and shall come forth to deceive the nations which are at the four corners of the earth, that is, Gog and Magog, to gather them for battle, the number of whom is as the sand of the sea. And they moved up onto the broad expanse of the earth and surrounded the camp of the saints and the beloved city. And a fire of God fell from heaven and devoured them. And the devil that deceived them was cast into the lake of fire and brimstone where the beast and the false prophet are, and they shall be tormented day and night into [the eons of the eons] the ages of the ages." (Revelation 20:7-10)

"And whosoever was not found written in the book of life was cast into the lake of fire." (Revelation 20:15)

The meaning of Revelation 20 is that Satan and implicitly, all those who haven't submitted to God by the end of the Millennium will be cast into the lake of fire. There Satan and the wicked will be punished for their rebellion. In addition to punishing, the lake of fire will also test, prove, and refine those in it. However, this process is not eternal as we understand the concept.

To verify this, let's look closely at the often misinterpreted final phrase in verse 10 of Revelation 20 "forever and ever." This phrase translated from the Greek "eis tous aionas ton aionon", literally means "into the ages of the ages." The Greek nouns aionas and aionon are plural forms of the Greek aion, which simply means eon or age. This word refers to an indefinite period of time; however, it does not convey the idea of eternity.

A correct understanding of "into the ages of the ages" shows that Satan, as well as those who worship the beast (Rev. 14:11) will be refined in the lake of fire for an indeterminate, probably lengthy, but still finite, amount of time.

Therefore...

"Be self-controlled, be watchful. Your adversary the devil, prowls around like a roaring lion, looking for someone to devour. Resist him, being steadfast in faith, yea knowing that the same kinds of sufferings are being accomplished in your brethren throughout the world." (1 Peter 5:8-9)

James gives believers advice on thwarting the devil's schemes:

"Therefore submit to God. But resist the devil and he will flee from you. Draw near to God, and He will draw near to you. Cleanse your hands, ye sinners, and purify your hearts, ye double-minded." (James 4:7-8)

Paul, in his second letter to Timothy, speaks of those who have been caught by the devil:

"But a servant of the Lord must not quarrel but be gentle to all, apt to teach, forbearing, in meekness correcting those who are in opposition, that God might grant them repentance, so that they may come to know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to at his will." (2 Timothy 2:24-26)