Catholic Doctrine, Clear And Simple: There Is Only One God

MANY SAY:
“God is a cosmic force.” “We should honor the god(s) of different races and religions.” “God exists according to one’s own perception.” 

BUT, THE CHURCH TEACHES:
There is only one God. “I am the first, and I am the last, and besides me there is no God” (Is.44:6). There can only be one God, because only one can be supreme, all-powerful, and independent of all.

In God there are three Divine Persons—the Father, the Son, and the Holy Spirit. By the Blessed Trinity we mean one and the same God
in three Divine Persons. 

The Father is God and the First Person of the Blessed Trinity. Omnipotence, and especially the work of creation, is attributed to God the Father.

The Son is God and the Second Person of the Blessed Trinity. To God the Son we owe our redemption from sin and eternal death; by
His death He gave us life.

The Holy Spirit is God and the Third Person of the Blessed Trinity. He manifests Himself in us particularly in our sanctification.

(source: My Catholic Faith by Most Rev. Louis La Ravoire Morrow)