To understand the "trinity" of Christian theology, we can understand it from the first chapter of Genesis, "Theology".
God is a spirit, and man is invisible. Before the creation of heaven and earth, the Father, the Son and the Holy Spirit were one. "My father and I are one" is the truth.
When God created heaven and earth, he realized it in the form of "talking".
In order to create heaven and earth, the son was born from the father with his unique position, which has all the characteristics of God. This is the Tao. Through the Tao, the Father created all things in the heavens, including us. In order to save people, the Tao became flesh (the Tao became flesh), and that is Jesus Christ. Therefore, the son was not born when Mary was born, but at the moment when his father "said". This is what Jesus said. He has long known the prophets in history. This process is also a process of "father sending son". Because the son has the characteristic of "coming out from the father", the father is the son. As long as heaven and earth do not waste, he will always be a son.
In the whole process, the Holy Spirit also carries all the characteristics of God, connecting (not communicating) between the Father and the Son to accomplish these tasks together.
On Pentecost, after the resurrection and ascension of Jesus Christ, the Holy Spirit, as the third God, was sent to the world by the Son (including the Father) (it should be sent by Jesus Christ, and the Holy Spirit is also called "the Spirit of Jesus Christ"), which became the witness (seal) of all people who believed in the name of Jesus Christ and was regarded as "one spirit". People all over the world are also divided into "people with the Holy Spirit (Christians)" and "people without the Holy Spirit (ordinary people)". Because of the existence of the Holy Spirit, Jesus Christ is in them, and Christians are United with Jesus Christ.
In the future, Jesus Christ will come to the world again, and will be distinguished by the presence or absence of the seal of the Holy Spirit.
From the action of "speaking", we can easily see that when the father speaks, the voice (child) comes from the father's mouth, and the voice carries meaning and emotion (holy spirit), so everything in the world is created according to the father's meaning. It would be terrible if what we say can't be said according to our wishes and can't convey our meaning. Therefore, the son was born in absolute obedience to the father, and the holy spirit also completely obeyed the father and the son to complete his work.
As a god, human beings also have the ability to speak with language, which is different from animals. Don't we speak just to make people understand and get what we mean? Genesis interprets the Trinity as "theism" in such a unique way.