How does God exist?

Some musings arising from my reading for the Philosophy for Theology course. I am very much still thinking these things through, so please consult an actual theologian if you have any high-stakes questions on the existence of God.

If one hangs out near the classical theism water-cooler for long enough, one is likely to overhear, as I myself have overheard, that God is identical to his own pure act of existence. What exactly does that mean?

Existence & essence

The most basic thing that all beings have in common is that they all exist. This is true for God himself and for each and every being that he made. They all participate in various ways in the act of existence. While we might think of being as a static quality that beings have, for St Thomas, being is fundamentally understood as an act that a being does. To be, after all, is a verb.