SSS
Everyone is hazy on the nature of the Trinity. It's a mystery
St Augustine spent the better part of his adult life writing on theology, and is considered one of the greatest theologians in history. He recorded that one day he was walking along the beach and saw a child dipping a spoon into the ocean and pouring the water out onto the sand. He asked the child what he was doing, and the child responded that he was attempting to empty the ocean. Augustine replied that it was impossible to empty the ocean with a spoon. The child in turn responded that it was far more likely that he would be able to empty the ocean with a spoon than for Augustine to ever comprehend the Trinity. It is noted that Augustine was so discouraged by those words, and the superficalness of all he had written, that he gave up writing altogether.
The Trinity is three seperate beings who are actually one, sharing a constant flow of love back and forth between each other. Thats a shallow description, but the best that can be managed. A marriage is a uniting of two seperate people to become one for the same purpose, with any child fruit of that marriage representing the completion of that trinity.