God in general is usually defined as the supreme being or the ultimate entity which possesses great powers and can influence and subdue anything to it's will.
God or gods are normally a vital, central part within religions with specific beliefs. Religions can have one god where it is usually defined as the creator of all things (as in Christianity) or even many gods, where they can be defined as supreme masters of a part of existence (like Poseidon, god of the sea from Greek mythology). A common fact about religious gods is that they cannot be directly seen or experienced in the physical reality. Therefore one has to have a belief or faith in a god in order to create an experience for self where one believes that the god exists and is 'real'.
The term god can also be applied or used to describe physical manifestations of this world with similar characteristics as described above. As for example: money as god of men, where it seemingly carries the power to decide between life and death of a person and everything in-between, just by it's presence or lack thereof.