Simply put, a Christian is a disciple of Jesus (Yeshua) the Christ or a follower of Christ Jesus.
To be a "Christian" one must be "born again", which means one must be born of water and of the Holy Spirit. As spoken in the Holy Bible, "Believe and be baptized and you shall be saved, but whoever does not believe shall be condemned." Mark 16:16
Please see John 3:16 "For God so loved the world that He gave His only begotten Son, that whoever believes in Him shall not perish but have eternal life."
Christianity is not a religion - it is a way of life.