Presuming god does exist (which is easiest for me as i do believe in him), he most likely exists outside our dimensions or our universe altogether. Otherwise, you would have a paradox of a creator creating himself via creating the universe. As we cannot perceive that which is outside our universe, we cannot truly know what god is.

To some, god is a being like man but perfect. To Dante, he described him as perfect geometric circles, if i correvtly remember my Paradiso. To presume to be able to describe him in any way is nigh on impossible for me. I have faith he spoke the universe into being with his Word, and that He exists, but what spoke the Word, i would never strive to define that being, let alone prove such a being exists or not.