"Rise and hurry to the Church: Here is the Father, here is the Son, here is the Holy Spirit.”
St Ambrose
The dogma of the Holy Trinity is a gift from God to man: it is God’s self-disclosure communicating the reality of his inner life of love.
The Catholic definition of the Trinity is the belief that God is one being, but made known to the world as three distinct persons: God the Father, God the Son, and God the Holy Spirit. The Trinity is a central doctrine of the Christian religion and a fundamental belief for Catholics.
The Trinity is a mystery, meaning that Catholics can never fully understand it. Some ways of understanding the Trinity include:
The Father: God the Father is the creator of everything and the Lord over the universe.
The Son: God the Son is Jesus, the son of Mary, who came to earth as a human being.
The Holy Spirit: God the Holy Spirit refers to the power of God in daily life.
The relationship between the Father and the Son: The Father eternally begets the Son, so there was never a time when the Father was without the Son.
The Trinity as a representation of love: The Trinity represents the Father’s and Son’s perfect love for one another.
The Nicene Creed clearly states the belief in the Trinity. The sign of the cross is a trinitarian prayer that demonstrates the importance of the Trinity.
The Blessed Trinity
From Catholic Encyclopedia
"Father, Son, and Holy Spirit" are titles
Titles used in the Catholic tradition to describe the Christian doctrine of the Trinity
Holy Spirit: God lives in our hearts
The Trinity is the central doctrine of the Christian religion, which states that God is one being in three distinct persons. These three persons are coequal, coeternal, and consubstantial.
Some say that the Trinity is a mystery and that one should stop trying to understand it and just believe. Others compare the Trinity to an egg, where the yoke, albumen, and shell are three elements that form one egg, just as the three members of the Trinity make up one God.