God is commonly described as a being who is omniscient, omnipotent, and so forth. Hegel says this is already a mistake. If God is to be truly infinite, truly unlimited, then God cannot be ‘a being’, because ‘a being’, that is, one being (however powerful) among others, is already limited by its relations to the others. It’s limited by not being X, not being Y, and so forth. But then it’s clearly not unlimited, not infinite! To think of God as ‘a being’ is to render God finite.
But if God isn’t ‘a being’, what is God? Here Hegel makes two main points. The first is that there’s a sense in which finite things like you and me fail to be as real as we could be, because what we are depends to a large extent on our relations to other finite things. If there were something that depended only on itself to make it what it is, then that something would evidently be more fully itself than we are, and more fully real, as itself. This is why it’s important for God to be infinite: because this makes God more himself (herself, itself) and more fully real, as himself (herself, itself), than anything else is.