What is Christianity?

What does it mean to be a Christian? What is this "walk of faith" supposed to look like anyway? Will people know I am a follower of Christ just by observing me? Can they tell by my words and my actions that Jesus is the most important person in my life?
Is being a "good Christian" just fighting my desires so that I can please God?
Or is it that by surrendering myself totally to God's will and purposes for me in my life He will bring me the most pleasure here on earth and for all eternity?