What Does Jesus Have To Do With Christianity?

"Do I have to believe in Jesus to be a Christian?" asked a young man whose Russian Jewish background had never exposed him to the Gospel.  Having been raised in a home in the former Soviet Union where God was seldom if ever discussed, he had heard about Jesus but didn't really know how He would fit into Christianity.  He wanted to know. How would you answer that question?  There are millions of people whose backgrounds are nominally Christian who still don't understand the relationship between Jesus Christ and Christianity.