Lol just so you know right now this represents my brain of trying to understand the Trinity. XD
Don't worry, the doctrine of the Trinity isn't about us trying to explain God, no one can explain God, He's God. What the doctrine of the Trinity is is the Christian Church affirming the truths which God has revealed to us, specifically our confession of these things against false opinions.
In the ancient Church there were a number of occasions where some people attempted to try and explain God, and that resulted in them saying some very wrong things--things which not only flew in the face of Scripture and the received faith of the Church but which implicitly denied the Gospel.
As such it was in many cases more important for us, as Christians, as the Church, to say what we do not believe.
For example, in the 2nd and 3rd centuries we have people like Paul of Samosata, he taught that Jesus was an ordinary man who upon his baptism by John was adopted as God's Son, and thus Jesus was a man who became divine, and after He rose and ascended into heaven was made a god by God. The response by the Church was that no, we do not believe this, for we confess that in the beginning was the Word, and the Word was with God, and the Word was God (John 1:1) and this Word who is God became flesh (John 1:14), and so on. And so the Church rejected Adoptionism as heretical, as a deeply false opinion. On the other hand, there were those, such as Sabellius, Praxeus, and Noetus who taught that God temporarily manifested as a human being, as Jesus, and that the one God (the Father) wore different masks, like an actor changing wardrobe in a play. The Church, again, said no we do not believe this, for we confess that at Christ's baptism the voice of the Father was heard from heaven, and the Holy Spirit descended upon Jesus as a dove (Matthew 3:16-17), and the Lord regularly pointed to the Father, and to the Holy Spirit, Jesus says in John's Gospel that He would ask the Father, and Another Comforter, the Holy Spirit, would be sent (John 14:16-17). And so on and so forth. And so the Church rejected what's called Modalism.
So that meant two views, in a sense on two ends of the spectrum, two extremes as it were, are being rejected.
In the 4th century an Egyptian presbyter named Arius was so anti-Modalist that he began teaching that Jesus was a second God, created by the Father. Thus there were two Gods, the eternal and uncreated Father, and a created, lesser God, the Son. Arius was so adament about rejecting Modalism that he ended up denying the eternity of Jesus and claiming that there were in fact two Gods. The Church, again, responded by saying that no, we don't believe this. As we confess that there is only one God, as it is written, "Hear O Israel, the LORD your God, the LORD is one" (Deuteronomy 6:4) and "I alone am God and there is no other" (Isaiah 46:9).
The result of this controversy is what led to the Council of Nicea, and the Nicene Creed. A few decades later another council, the Council of Constantinople would meet to address two other controversies, and provide us with the current text of the Nicene Creed which we still read and confess today.
So this is what we see, historically, not so much a, "We are going to explain God", but rather we reject what is false, and that leaves us with confessing the truth. So the doctrine of the Trinity is not about understanding or explaining God, but about confessing God as God Himself has given Himself to us.
It's not an easy idea, it's a very complicated idea. But anytime we try and simplify it, we end up saying things that are deeply and troublingly wrong.
So where do you get this idea from then?
It's important to understand that from the beginning there have always been living, worshiping, believing communities of Christians. The communities we read about in the New Testament continued to practice their faith, and to worship, and they continued to abide in the teaching and preaching of the Apostles.
Because of this, that means there has always been a living stream of teaching and faith that has come down through the centuries. And so when we find various pious opinions and ideas which aren't necessarily found in the Bible, it's because these ideas are part of the living, active Christian communities throughout the Christian world.
There have always been debates, discussions, and arguments over certain ideas. That's just part of the history, the story, of Christianity down through the ages.
But when
@RushMAN says he gets this idea from the Church (and later you ask where did the Church get it), this is more-or-less what is meant. These ideas exist within living, believing communities of Christians, and these ideas, beliefs, practices, etc are passed down from one generation to the next. In fact this is how we got the Bible itself, because the Bible, as a bound volume of different books of Scripture, didn't just show up out of no where, it grew out of the practice and preservation of Christian faith and teaching down through the centuries, until it was then also passed on to you and me.
Now, that does raise questions--namely over the verity of certain positions, of certain ideas. And, obviously, the disagreements over these very things are why Christians are divided today. But recognizing this can be very helpful in understanding ourselves and our own place, at present, in the ongoing story of Christianity even today.
-CryptoLutheran