There is one true and living God. God is three persons: God the Father, God the Son and God the Holy Spirit. The Father, Son and Holy Spirit are distinct Persons and each is God. Yes, they are not three gods, but one God in three Persons, usually called the Trinity. The Bible clearly teaches that God is three Persons, so we believe it, even though we can't completely understand it.
The Bible speaks about all three members of the Trinity from the beginning of Genesis to the end of Revelation. Jesus clearly taught about all three in John 15 and 16.
Our minds can't completely understand how one God can be three Persons, because the Trinity has unity that is much greater than any unity people can have. Although God is three Persons, He is one, in perfect unity of purpose and love. If we study what the Bible teaches about each member of the Trinity, it will help us understand this truth more clearly.
God the Father is our Creator. He is the maker of the universe and the giver of all life. God the Son (Jesus Christ) is our Savior. He became a man to show the world what God is like. He paid the penalty for our sin and has provided everlasting life to anyone who will receive Him.
God the Holy Spirit is our Helper. He is always with us because He is in each person who has received Jesus Christ as Savior. He helps us receive God's forgiveness and obey Him in our daily lives.
Each member of the Trinity is working in the world and in our lives. Though God the Father is our Creator, the Bible teaches that Jesus and the Holy Spirit also had a part in creation. Jesus, God's Son, is our Savior, but the Father and the Holy Spirit also are involved in the work of salvation. The Father and Son work in our lives to help us as the Holy Spirit does. Each member of the Trinity is an individual Person, but they think and act together and can't be separated.