What does it mean to be a Christian?

I was in Sunday School. Across from me sat this guy who grew up in the ghetto. He liked questionable music, questionable women, was into the drug scene, dressed like a player, talked like a hood. I remember thinking, "I don't think my life is really any different than his. There's probably not a thing he would do that I wouldn't."

What does it mean to be a Christian?
What does it mean to follow Jesus?
What does it mean to be saved?