When we speak of God, we speak of three Persons. But we speak of only one God.
The joke that I have used with youth is to say that the Trinity consists of “three who’s, one what, two processions, and two missions.” There are three divine Persons – Father, Son, and Holy Spirit. Yet, all are God and share the same nature (the same “what”). The Son was begotten of the Father. The Holy Spirit proceeded from the Father and the Son. Both can be called processions. Those processions are internal to God. Or some might say internal to the Godhead. Both happened before time began. Missions are where God entered our world at a point in time. These two visible missions are Jesus’ Incarnation (including his entire life on earth) and the Holy Spirit at Pentecost. They are where God entered our world such that we could see it happen.
Any human description of the Trinity with our finite human language is necessarily an incomplete explanation of an infinite God. But such explanations are helpful for us.
Jesus’ mission was primarily to save us. But, in so doing, God entered our world. Creator becomes creature. Jesus makes God visible to us. He reveals the Father to us. We can see God because we can see him.
God told the Israelites not to worship graven images. They had no image of God because they had not seen God. Then the Father sent the Son. And the world had an image of God. An image in human form. We do not worship artistic representations of God. We only worship God. But an artistic image calls to mind what we worship.
Yes, we know a lot about God from the prophets that he sent. But our primary source of information about God is God. The Son tells us about the Father. The Son tells us about the Holy Spirit. It is through the Son that God is revealed to us most fully.
In many other religions, there is a figure that purports to tells us about God. In Christianity, it is God that comes to tell us about God. We start with who Jesus is. What he says is so important because of who he is.
Have we ever simply sat and wondered about a God that chooses to become one of us? What do we think of God because of that? What do we think of ourselves because of that?