The root word of “Christian” is Christ, which comes from the Greek (language of the New Testament) word christos, meaning "anointed one" or "chosen one.” When we say “Jesus Christ,” Christ is not the last name (surname) of Jesus. It is His title, as in Jesus the Christ. It means that Jesus is sent from God as a king and deliverer (and He Himself is God).
The word “Messiah” means the same thing as “Christ,” except it is from Hebrew, the language of the Old Testament.
A Christian is someone who is a follower of Jesus Christ.