Thank you for your question, and I hope you will always be interested in what the Bible says–not just about the devil, but about God and His love for you.
The Bible doesn't tell us exactly what the devil looks like; the pictures you see of him (with horns and a red suit and so forth) simply come from the artist's imagination. Similar pictures have been around for hundreds of years, however, and were meant to warn people about Satan. Satan is evil, and even these pictures should warn us not to have anything to do with him.
Satan, the Bible says, is totally evil–and yet he can disguise himself so people don't even realize who he is. In fact, the Bible says that sometimes "Satan himself is transformed into an angel of light" (2 Corinthians 11:14, KJV). Satan's goal is always to stop God's work. He tried to stop Jesus from going to the cross for our sins, and he will try to keep you from God.
Satan is real–but don't concentrate on him. Concentrate instead on Jesus, because He is stronger than Satan, and by His death and resurrection He defeated Satan. The Bible says, "The reason the Son of God appeared was to destroy the devil's work" (1 John 3:8). Ask Jesus to come into your life today because God loves you and Jesus wants you to walk with Him every day.