John 1:14: The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the One and Only who came from the Father, full of grace and truth.
John 10:30: "I and my Father are one."
Philip said, “Lord, show us the Father and that will be enough for us.”
“Jesus answered: “Don’t you know me, Philip, even after I have been among you such a long time? Anyone who has seen me has seen the Father. How can you say, ‘Show us the Father’? Don’t you believe that I am in the Father, and that the Father is in me? The words I say to you are not just my own. Rather, it is the Father, living in me, who is doing his work” (John 14: 8-10).
John 16:7 . . . I am going away. Unless I go away, the Counselor (Holy Spirit) will not come to you. . . .
Most of the Gospel According to John, as well as excerpts from other scripture, makes the case for the Doctrine of the Trinity that was developed by theologians in the Second Century. That Doctrine was not created out of thin air but came from understanding of who Jesus of Nazareth actually was and the supernatural aspect of his being.
That Doctrine was never conclusively decided and debates over it tore the Church apart for centuries and, to some degree, continues to be a point of contention.
I believe most Christians, including myself, however discern the truth as being something like this:
1. God the Father is the Creator. All that has ever been, is, or will be came forth from Him.
2. In order for humankind to be able to love and experience joy, however, it was necessary for God to give humankind free will. That free will enables us to feel and experience all the glory and wonders that God has to offer, but it also enables us to do harm to ourselves and/or others. (My defintion of sin.) Because there are always consequences for sin, a Redeemer was necessary.
3. To show humankind their error in attempting to achieve redemption through keeping rules and regulations, something impossible to do for those with free will, God became flesh and lived among us, fully human with ability to feel and laugh and hurt and bleed as any human. In this form He is Jesus, the Son.
4. When He had completed his ministry on Earth, a human ministry that was of necessity limited to a small area and a relatively small number of people, He left and came back as the spirit Counselor to those He had prepared to receive it. And thus God remains with us ever since.
So there you have God the Father, God the Son, God the Holy Spirit, three in one, all one being but in different forms.
My best explanation however inadequate.