Western Christianity has a two-fold distinction by which it classifies all of reality. Either something is part of the divine essence, and thus fully God, or it is part of creaturely reality, and thus not God. This distinction seems to be quite important to maintain since Scripture teaches that God is transcendent and completely "other" from the rest of his creation. One's options become extremely limited, however, when for example Peter tells us that we as Christians are "partakers of the divine nature" (II Peter 1:4). How ought we classify this "nature" that we are partaking of? Forcing one to choose whether we partake of God's essence or not has lead to two extremes: either God is totally inaccessible (hyper-transcendence) or he is part of creation after all (hyper-immanence). Typically, the latter option is taken leading to such notions as divinization, where we as creatures become divine, or pantheism, where God is becomes part of creation.
Michael Horton has found in Eastern theology a helpful solution to this conundrum. Of the two-fold distinction which I mentioned, Eastern Christianity has always had a third option, that is, the energies of God. Divine energies are God's words and works whereby he interacts with his creatures. They are not part of God's hidden essence nor are they simply part of his creation, but as the rays from the sun are not part of the sun itself nor part of the world it's illuminating, so also God's energies deserve their own classification. Furthermore, the East has been careful to maintain that we as Christians do not experience God according to his essence, but rather, through his energies. Thus his power, love, glory and grace... are what we partake of and know, not his very essence. God reveals himself to us through his energies.
Reformed theology shares this notion with its emphasis upon the covenant. It teaches that God has chosen to interact with his creatures only by way of covenants and thus we as his people know God through his words (oaths, promises, commands, threatenings, consolations, etc.) and his works (creation, preservation, redemption, etc.). We do not and cannot know God according to his essence, but rather what he has revealed to us about himself (Duet 29:29). God is with us in that he is God for us, the God-in-action who is moving redemptive history along.