The Catechism in Questions & Answers

66. What is the relationship of the Father, the Son, and the Holy Spirit to one another?

Father, Son, and Holy Spirit are names for the three divine persons. Although they are to be distinguished from one another, they are nevertheless the one God.
In Christian tradition, each of the three divine persons is assigned a particular point of emphasis: God, the Father, is the Creator of heaven and earth.
God, the Son, is the Redeemer who became human and gave His life as a sacrifice for the redemption of mankind. God, the Holy Spirit, is the Maker of the new creation: He sees to it that the salvation of God is made accessible to mankind and that the new creation comes to its completion.

New creation: see Questions 528. et seq.