Christos is the Greek word for the Anointed One — the exact equivalent of the Hebrew Messiah. It is not a surname but a title: to say Jesus Christ is to declare Jesus the Christ, the long-promised King and Deliverer anointed by God. Kings, priests, and prophets were anointed in the Old Testament, and all of it pointed forward to the one who would be Prophet, Priest, and King in full.
Peter's great confession — Thou art the Christ, the Son of the living God — is the hinge of the Gospels. To believe that Jesus is the Christ is the heart of Christian faith; John wrote his Gospel that we might believe exactly this, and believing, have life in his name. Christos names the fulfilment of every ancient hope.
Christos in Scripture
And Simon Peter answered and said, Thou art the Christ, the Son of the living God.