The True Definition of a Christian. The reason you are a Christian is not because you do good things like go to church or read the Bible. It is not because you were raised in a “Christian” home or nation. It’s not even because you believe in the concept of God. It is because you believe that Jesus Christ is the Son of God, the Savior of the world, and the King that will reign for eternity. Your faith in Jesus is what makes you a Christian—pure and simple.