Satan is not the devil's name but his job description; it is Hebrew and means 'Adversary', while devil is from the Greek diabolos and means 'Slanderer'. The Bible tells us that the angels were created as ministering spirits for the heirs of salvation and that one of these was a mighty spirit being called 'Helyel Ben Shachar', or 'Light Bringer, Son of the Dawn'. The medieval translator Jerome rendered 'Light Bringer' in Latin as 'Lucifer', which has stuck ever since. We also know that he was created perfect and of an exalted class of spirit known as the Cherubim.
Join the dots and we can see that Lucifer was created to serve mankind, which is what he was supposed to be doing in Eden. But something happened. We know that this was before he fell, because Yahweh Elohim looked onall he had created and called it 'very good', which it could not have been had Lucifer already fallen. We also know that sin and death entered the universe through Adam and not Satan, so Satan did not fall before Adam. So when did he? The answers all tie together when we understand that God created Adam in his own image and after his likeness, and gave him all dominion and authority on earth. A comparison between some New Testament promises to man, with some Old Testament claims by Lucifer show that Lucifer coveted man's position and ultimate destiny to rule at God's right hand forever, so he worked out a strategy: Discredit Adam and take his place.
This he would do by tempting Adam to disobey the one law that existed in the whole Universe: 'Do not eat the fruit of the tree of the knowledge of good and evil.'
Lucifer reasoned that man had one weakness, an immature proclivity to resist being told what to do, not because he was sinful, but because he was created royal, in God's image and likeness, with a will to dominate and not be told what to do. By appealing to this sense, Lucifer succeeded in tempting man to sin, but failed to foresee that this meant he inherited a poisoned chalice of his own making. Before man disobey God, there was no sin, death, condemnation or judgement in the entire Universe: Now there was, and Lucifer was now subject to it. 'The road to hell', as they say, 'is paved with good intentions', and Lucifer appears to have believed that betraying mankind was doing God a favour, but he deceived himself and it cost him his position and made him our Accuser and God's Adversary.