Christians do not or should not believe in three Gods, they believe in One God in three ‘offices,’ ‘facets,’ or ‘aspects,’ or, revealed in three different ways.
1st ‘facet’ or ‘part’ of the Trinity
God (Yehovah ‘Elohim = The Lord God), is the Father, the One and Only God Eternal! He whom created everything, He whom has no beginning and has no end.
14 And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.
15 And God said moreover unto Moses, Thus shalt thou say unto the children of Israel, The LORD God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, hath sent me unto you: this is my name for ever, and this is my memorial unto all generations. (KJV)
2nd facet of the Trinity
Jesus Christ of Nazareth is the Son (Yehoshua = Yehovah the Savior, or, God Savior), He is God manifested (came) in the flesh, He is God in human form come to earth to save His creation from satan and their sins. Jesus is not another God, He is God.
John 10:27-30 (Jesus speaking)
27 My sheep hear my voice, and I know them, and they follow me:
28 And I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand.
29 My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father’s hand.
30 I and my Father are one. (KJV)
3rd facet of the Trinity
Holy Spirit (tó pneúma tó hágion = The Spirit The Holy = The Holy Spirit) is the Holy Spirit of God. The Holy Spirit is the Power of God in action. It is through the Holy Spirit of God that God interacts with His creation today, for He no longer walks with man face to face as He did with Adam, Noah, Abraham….., and He no longer is physically amongst us as He was when Jesus Christ walked the earth. This is because we (as a peoples) fell short, we forsook Him, we left Him — He didn’t leave us! Below we see that the Holy Spirit is the Spirit of God, God’s Spirit; not a separate ‘person’ or individual apart from God: