God can be many things. When it is just referred to as God you are thinking of the Christians God who by Christians like myself believe created everything in the beginning of time. But beforehand there have been belief in other gods such as Bhudda in the Bhuddist religion, or the same god in the Jewish religion which proceeded Christianity. The Romans, Greeks, and Trojans all believed in the same gods and goddesses, however, the Romans just used Latin names. The Babylonians believed in other gods that were more powerful and created the universe.
With beliefs in God and other gods the possibilities are endless, you never know what someone is going to believe.