do Christians know what being Christian is?
Not many do...
Jesus answered, The work of God is this: to believe in the one he has sent.
1 John 3:21-24
Dear friends, if our hearts do not condemn us, we have confidence before God and receive from him anything we ask, because we keep his commands and do what pleases him. And this is his command: to believe in the name of his Son, Jesus Christ, and to love one another as he commanded us. The one who keeps Gods commands lives in him, and he in them. And this is how we know that he lives in us: We know it by the Spirit he gave us.
Apparently at least 20% do not, though we all should do better in living out the faith.