We believe in one God: the Father, the Son, and the Holy Spirit. The three are distinct persons, equal and eternal, sharing one undivided divinity, will, power, and glory.
What the Church teaches
The Father is unbegotten, the Son is eternally begotten of the Father, and the Holy Spirit eternally proceeds from the Father. These names reveal real relations, not ranks of greater and lesser divinity. Every divine work is the work of the one God, yet Scripture reveals the three persons—for example at Christ’s baptism and in the command to baptize all nations.
Live it this week
Pray the Trinitarian invocation slowly and trace where the Father, Son, and Holy Spirit are named in the Creed and Divine Liturgy. Memorize Matthew 28:19 and ask a teacher to explain one Trinitarian prayer from the liturgy.
When personal guidance matters
The Trinity is not three gods, one person wearing three masks, or three parts that combine to make God. Created analogies may point toward one feature, but none can contain the mystery and each must be used carefully.
Sibhat prepared this original answer from the sources listed above. For personal or sacramental guidance, speak with your parish priest.