Answer
In light of the teaching that God is one and that all three persons are divine, the only explanation that could emerge is the doctrine of the Trinity. So, theologians throughout history have handled this using two terms; the "ontological Trinity," which is a very philosophical term that has to do with the essence of God—God in essence is three persons—and the "economic Trinity" that has to do with its function and the idea that these three persons have had three distinct principal functions. Not that they did not all participate, for example, in creation. All three participated. In salvation, all three persons are involved. In the Christian life, the three persons are active, but each with a different function. Now, there are people who favor only the economic or functional Trinity, and they think, well, God is one, but he functions in different ways. And this can lead us to deviate from the biblical teaching because the Bible does not talk about God's modes of operation, but it speaks of three distinct persons: the ontological Trinity, the Trinity in essence. The three persons exist in reality. They're not just operating modes of one God, but they are three persons, and of course, each one has his functions. So, we must always affirm these two things in a balanced way. Or we might call the essential Trinity instead of ontological so we don't sound too technical, and the functional Trinity rather than saying the economic Trinity, which is sometimes not a very clear term. So, I prefer to use "Trinity in essence" and "Trinity in function," and to affirm the two things in a balanced way.