Satan began his existance as an annointed Angel named Lucifer.  Satan made war with God and attempted to take over heaven, convincing a third part of the Angels to follow him.  Ultimately Satan, who is  also refered to as the Devil and the dragon, was unsuccessful and was cast down to the Earth.

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

How art thou fallen from heaven, O Lucifer, son of the morning! how art thou cut down to the ground, which didst weaken the nations!  For thou hast said in thine heart, I will ascend into heaven, I will exalt my throne above the stars of God: I will sit also 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]

And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.  [Revelation 12:4]

And he said unto them, I beheld Satan as lightning fall from heaven.  [Luke 10:18]

Satan, through a serpent, tempted Eve in the Garden of Eden with a lie and Eve, followed by Adam, committed sin for the first time because of this temptation.

Now the serpent was more subtle than any beast of the field which the LORD God had made. And he said unto the woman, Yea, hath God said, Ye shall not eat of every tree of the garden?  And the woman said unto the serpent, We may eat of the fruit of the trees of the garden:  But of the fruit of the tree which is in the midst of the garden, God hath said, Ye shall not eat of it, neither shall ye touch it, lest ye die.  And the serpent said unto the woman, Ye shall not surely die:  For God doth know that in the day ye eat thereof, then your eyes shall be opened, and ye shall be as gods, knowing good and evil.  And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.  [Genesis 3:1-6]

Satan is the great deceiver and the adversary of God and of  all of the Children of God.  He is the father of lies and the author of deception.

Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it.  [John 8:44]

In olden times, Satan was able to accuse the Children of  God before God.  However, through the power of Christ he has been cast down and much of his power is curbed.

Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.  [Job 1:6]

And I heard a loud voice saying in heaven, Now is come salvation, and strength, and the kingdom of our God, and the power of his Christ: for the accuser of our brethren is cast down, which accused them before our God day and night.  [Revelation 12:10]

Satan still has a great affect on the World today.  He goes forth to spread lies and falsehoods.  Only through the truth and power  of Christ are we able to overcome him.

He that committeth sin is of the devil; for the devil sinneth from the beginning. For this purpose the Son of God was manifested, that he might destroy the works of the devil.  [1 John 3:8]

To whom ye forgive any thing, I forgive also: for if I forgave any thing, to whom I forgave it, for your sakes forgave I it in the person of Christ;  Lest Satan should get an advantage of us: for we are not ignorant of his devices.  [2 Corinthians 2:10-11]

Satan was created as an Angel of light but through his own pride he rose up against God and was cast down to Earth.  Satan remains on Earth today, seeking to deceive and corrupt mankind.  Only through the power of Christ are we able to resist this temptation and refrain from sin.