The Bible teaches that the Father is God, the Son is God, and the Holy Spirit is God. So, God is one being Who has existed eternally as three distinct, not separate, Persons. As distinct Persons, each functions in His own unique manner. The Father is the Originator, the Son [Jesus Christ] is the Agent, and the Holy Spirit is the Applicator. Each Person is self-conscious and self-directing. Yet one Person never acts independently or in opposition to the others.
All three Persons were involved in creation. It was "in Him" [Jesus Christ] that God created all things (Colossians 1 v 16), and the Spirit of God hovered "over the waters" (Genesis 1 v 2).
In salvation, God [the Father] loved the world so much that He gave His one and only Son (John 3 v 16). After Christ's resurrection from death, and His ascension into Heaven, both He and the Father sent their promised Holy Spirit to be our Comforter and Guide (John 14 v 16 & 16 v 7).
The distinction between the three Persons was evident at the time of Jesus' baptism. The Son [Jesus] comes up out of the water, the Holy Spirit descends in the form of a dove, and the Father declares, "This is My beloved Son, Whom I love; and in Him I am well pleased." (Matthew 3 v 16 - 17.
Jesus affirmed the Trinity when He commanded His disciples to baptise "in the name of the Father, and of the Son, and of the Holy Spirit." (Matthew 28 v 19)
One God in three Persons! In our God we have a heavenly Father Who loves us and sent His Son to die for our salvation from sin. In this God we have Jesus Christ, Who became one of us (Philippians 4 v 6 - 8), to take the punishment we deserved. In this God we have the Person of the Holy Spirit, our Helper and Divine Comforter, Who lives in us to give us victory over sin.
This triune God hears us when we pray, understands us when we suffer, and will see us safely home.
Adapted and revised from 'Do Christians Believe in Three Gods?' - Our Daily Bread Ministries 1992