Those who belong to Christ through faith and Baptism must confess their baptismal faith before men. First therefore the Catechism expounds revelation, by which God addresses and gives himself to man, and the faith by which man responds to God (Section One). The profession of faith summarizes the gifts that God gives man: as the Author of all that is good; as Redeemer; and as Sanctifier. It develops these in the three chapters on our baptismal faith in the one God: the almighty Father, the Creator; his Son Jesus Christ, our Lord and Saviour; and the Holy Spirit, the Sanctifier, in the Holy Church (Section Two).
Source: Catechism of the Catholic Church (Vatican.va)