The Anointed One — the Greek translation of Hebrew Mashiach (Messiah). In the OT, kings, priests, and prophets were anointed with oil as a sign of God's commissioning. Christos became the title — and eventually part of the name — of Jesus, the ultimate King, Priest, and Prophet.
Peter's confession — 'You are the Christ, the Son of the living God' (Matthew 16:16) — is the foundational Christian declaration. Jesus is the one in whom all OT anointing finds its fulfillment: He is the King who reigns forever, the Priest who offers Himself, and the Prophet who speaks God's final word. 'Christ' is not Jesus' last name but His title and mission. To say 'Jesus is the Christ' is to say: the long-awaited one has come.