One of the things that can be confusing for people is that God is mysterious because he is 1 in 3 - and 3 in 1 at the same time. Christians do not believe in three gods but in a single God who is also three - he is triune. Christians refer to this as the 'Trinity' or more often, the 'Godhead'.
There is God the Father; Jesus the Son; and the Holy Spirit. God is the Father, Jesus is the Son - together with the Holy Spirit, three in one.
The Bible consistently tells us that there is one God and that God is the Lord (often called 'Yahweh').
The Bible tells us that in the beginning, God created the heavens and the earth. In the original language, we learn that the word for God is 'elohim' which is plural.
The Bible also tells us that in Jesus is the fullness of the Godhead in bodily form. And we know that the Holy Spirit comes to live in the heart (or in the 'spirit of man') of anyone who believes that Jesus is Lord.
This is a mystery that we cannot fully understand - but it is important to know that Christians worship one God, not many gods.