What's the difference between the devil and a demon? Maybe it isn't very important, but I've always been curious about where evil comes from, and the devil, and things like that. — J.Y.
The first truth the Bible tells us about the devil is that he is real, and he is our enemy. Jesus said that the devil "was a murderer from the beginning, not holding to the truth, for there is no truth in him" (John 8:44).
This is one reason why I caution you not to become too fascinated with the devil or with evil. Satan's main goal is to turn us away from God—and when we focus too much on the devil, then we won't focus on God the way we should. Yes, the devil is real, and so are his demons (evil spiritual beings who carry out his commands). But God is also real—and He alone is all-powerful. And someday He will defeat Satan and bind him forever.
Instead, focus your attention on Jesus Christ. The Bible says, "The reason the Son of God appeared was to destroy the devil's work" (1 John 3:8). How did He do this? He did it by His death on the cross for us (which won our salvation) and by His resurrection from the dead (which conquered death and Hell). Satan is a defeated foe!
Have you ever opened your heart to Christ, and are you seeking the help of His Spirit every day to defeat Satan's temptations? Make sure of your salvation today by giving your life to Christ. Then make Him the center of your life, for He alone gives us victory over death and Hell and Satan.