The word “Christ” comes from the Greek translation of the Hebrew Messiah, which means “anointed”. It became the name proper to Jesus only because he accomplished perfectly the divine mission that “Christ” signifies. In effect, in Israel those consecrated to God for a mission that he gave were anointed in his name. This was the case for kings, for priests and, in rare instances, for prophets. This had to be the case all the more so for the Messiah whom God would send to inaugurate his kingdom definitively. It was necessary that the Messiah be anointed by the Spirit of the Lord at once as king and priest, and also as prophet. Jesus fulfilled the messianic hope of Israel in his threefold office of priest, prophet and king.
To the shepherds, the angel announced the birth of Jesus as the Messiah promised to Israel: “To you is born this day in the city of David a Saviour, who is Christ the Lord.”From the beginning he was “the one whom the Father consecrated and sent into the world”, conceived as “holy” in Mary’s virginal womb. God called Joseph to “take Mary as your wife, for that which is conceived in her is of the Holy Spirit”, so that Jesus, “who is called Christ”, should be born of Joseph’s spouse into the messianic lineage of David.
Jesus’ messianic consecration reveals his divine mission, “for the name ‘Christ’ implies ‘he who anointed’, ‘he who was anointed’ and ‘the very anointing with which he was anointed’. the one who anointed is the Father, the one who was anointed is the Son, and he was anointed with the Spirit who is the anointing.'” His eternal messianic consecration was revealed during the time of his earthly life at the moment of his baptism by John, when “God anointed Jesus of Nazareth with the Holy Spirit and with power”, “that he might be revealed to Israel” as its Messiah. His works and words will manifest him as “the Holy One of God”.
Many Jews and even certain Gentiles who shared their hope recognized in Jesus the fundamental attributes of the messianic “Son of David”, promised by God to Israel. Jesus accepted his rightful title of Messiah, though with some reserve because it was understood by some of his contemporaries in too human a sense, as essentially political.
Jesus accepted Peter’s profession of faith, which acknowledged him to be the Messiah, by announcing the imminent Passion of the Son of Man. He unveiled the authentic content of his messianic kingship both in the transcendent identity of the Son of Man “who came down from heaven”, and in his redemptive mission as the suffering Servant: “The Son of Man came not to be served but to serve, and to give his life as a ransom for many.” Hence the true meaning of his kingship is revealed only when he is raised high on the cross. Only after his Resurrection will Peter be able to proclaim Jesus’ messianic kingship to the People of God: “Let all the house of Israel therefore know assuredly that God has made him both Lord and Christ, this Jesus whom you crucified.”
From the Catechism of the Catholic Church 436-440