Who is God?
The Holy Trinity, 1630-1645, by Schelte Adams Bolswert, Flemish from the Philadelphia Museum of Art
There is one true God, who made the heavens and the earth and everything that is in them (Genesis 1).
This God has revealed himself to us through the Holy Scriptures as one God in three persons: Father, Son, and Holy Spirit (Matthew 28:19).
The Father created the heavens and earth and continues to sustain them and all of his creatures with everything they need (1 Corinthians 8:6).
The Son is the eternal Word of God through whom all things were made (Colossians 1:16). This eternal Word became a man in the person of Jesus to save all of creation from sin, death, and the power of the devil (1 Corinthians 15:56-57). After his earthly ministry, the Son ascended into heaven and sits at the right hand of the Father, interceding for us (Romans 8:34).
The Holy Spirit proceeds from the Father and the Son (John 14:26, John 15:26). He works in the Church, bringing people to faith in Jesus (John 14:26).
The Christian Church throughout history has confessed God as the Father, Son, and Holy Spirit in the words of creeds: specifically the Apostles’, Nicene, and Athanasian Creeds.
For more about the Triune God, read the Apostles' Creed and its explanation from the Small Catechism.