As many of my students will know, I love teaching trinitarian theology. This is not because I like solving conundrums, because I don't; it is because in the triune God we come face to face with reality; the Truth, with a capital T.
We cannot explain the Trinity. Many theologians have dismissed it as an irrelevance that cannot have any practical application to Christian life. In fact Emmanuel Kant said, "“Absolutely nothing worthwhile for the practical life can be made out of the doctrine of the Trinity taken literally.” I beg to differ! There are however, certain things we need to clarify.
Firstly, the Trinity is NOT a doctrine taught in the Bible; it is the work of the Church to try and understand the Triune God. God is revealed to us in the Bible as in three persons: Father, Son and Holy Spirit. The Trinity as a doctrine is the Church's attempt at understanding that reality.
Secondly, the words used in Greek (and Latin) to understand the Trinity do not have a direct equivalence in English or any other modern language. Three Hypostasis in one Ousia or Three Personae in one Substancia cannot really be understood as Three persons in one being. Scripture clearly refers to God as Father and as Son and as Holy Spirit. The baptismal formula of Matthew 28:19 is obviously trinitarian. God's actions God is reveals in plurality. "Let us make humanity in our image", God says in Genesis 1.In We know God through Jesus Christ. We know the Father as the God and Father of our Lord Jesus Christ and we know the Spirit as the Spirit of Christ.
Eastern Orthodox Christianity emphasises God as a community or a communion of persons. This is often referred to a the social Trinity. God is a community of love and purpose and it is in THAT image we, as human beings, have been created. It is for that reason we have been created. We have been created for community and love. This is why in Christianity God can BE love. Islamic philosophers quite rightly recognised that in Islam Allah cannot BE love. This is because, before anything was made, Allah had nobody to love. He would have had to create somebody to love.
In Christian understanding God, before anything was created was already a living and loving being because there was an "intra-trinitarian" love; i.e. within the Trinity. The Trinity make sense of human life and love.