So every once in a while you’ll hear Orthofolks speak of “essences and energies” and it all sounds sort of weird and esoteric, but what exactly is meant by this, and why is it important for us? The terms are most closely associated with St. Gregory Palamas; specifically in his interactions with Barlaam of Calabria, a humanist scholar and opponent of hesychasm (spoiler alert: his views were later condemned as heretical). It’s more than we need to get into here, but essentially (see what I did there?) St. Gregory said that the prophets had greater knowledge of God than ourselves because they had actually seen and heard God - the question was one of how mere mortals could claim knowledge of an unknowable and transcendent God.
Here enters the essence (ouisia) vs. energies (energeia) idea. You may recall the use of the work essence as it appears in the Nicene Creed we discussed previously. Basically, according to St. Gregory, and by extension, Orthodox theology, we cannot know God in His essence, i.e., God in Himself, but we can know God through His energies, i.e., what God does, who He is in relation to man and creation - because this is how God has chosen to reveal Himself to humanity.