The nature of God, the esence of God, what God is. It refers to what is and can not no-be. God is light and He can not no be light. If God ceased to be light, he seaced to be God; because God is light and not being light means not being God. The ecense of God, the nature of God, His hypostasis is what makes God to be God, and without it He would not be God.
God is sait, love, spirit, light and few more things. He can not no-be any of thouse things he is. And how do we know what God is? We know it because the Bible say so. We read that "God is love" Dont we?
What is catch? The catch is that many, way to many theologians have add to God things that He is not. For example: we read of the power of God. We read that nothing is impossible for Him. There is not any limitation on His power. We can surely say that God acts in a allmighty manner, that Hes potence is omnipotent. Then, many theologians conclude that God is almighty and omnipotent. Is Him?
The catch is that in the entire Bible we dont read of God being almighty or omnipotent. In fact, those words are not found in the Bible. If we focus on verses saying "God is..." we will not found Him as being almighty. The point is that the power is not an esence of God, is not what God is. God is not God because He acts with omnipower; God acts with omnipower because He is God. And God will continue to be what He is, even without that power. Because God being do not depend on how much He can do.
This is not irrelevant. We know that Jesus is God made flesh. That is not disputed. Nevertheless we found that Jesus was not almighty. In ocations he tryed to do thing, really tried, but "failed". We read that the power of God was on him; not that he had power of his own. And we see Jesus praying to the Father for him to perfor the power. This is very shoking for some christians. The question is if he is God almighty, how he dont have power? And the next is saying that if we denay him as almighty we denay his divinity.
Jesus is God. Period. Jesus was not almighty and he was (is) God. Because having omnipower or not is not what makes the fatjer to be God, nor makes the Son be God. The Son (Jesus) is the son despite not having omnipower. How? Simply because being or not being God do not depend on having or not having omnipower.
Christ had omnipower, but he emtied out of having omnopower and became man. Emptying himself of the omnipower is not emptying of being God or divine. Because being divine do not depend on the omnipower.
Same with the omnipresence and the omniknowledge. Jesus was not omnipresent nor omniscient. But he was fully God. He was fully God because the omnipresence, omniscienmce and omnipower is not what God is. Those things are not what God is. God has omnipresence, he has omniscience, and have omnipower. But those are not what make God be God.