When Psalms 91:1 refers to the secret place (in Hebrew: “b’seter elyon”) of the Most High, what is the secret place?

Whenever we talk about God, we obviously speak in poetic non-literal terms, for we obviously can’t “understand” Him, but we yearn to relate to Him, so we use words and concepts which we do understand. Here too, God as if it were, “He that dwells in a secret place” , which is similar to elsewhere (Tehilim 18, 12), “He made darkness His secret place…”. In other words these are different ways of saying that our monotheistic non-physical and perfect God is hidden from us, and we can’t understand Him and His Greatness.