Dungeons and Dragons
Deities are the most powerful immortal creatures, residents of the countless dominions that swirl through the Astral Sea. They appear in dreams and visions to their followers and wear countless different faces, and artwork depicting them shows them in a variety of forms. Their true nature is beyond any physical form. Corellon is often depicted as an eladrin, but he is no more an eladrin than he is a fey pantherhe is a god, and he transcends the physical laws that bind even angels to their concrete forms.
Some deities are good or lawful good, some are evil or chaotic evil, and some are unaligned. Each deity has a vision of how the world should be, and the agents of the deities seek to bring that vision to life in the world. Except for the chaotic evil gods (Gruumsh and Lolth), all deities are enemies of the demons, which would rather destroy the world than govern it.
Most people revere more than one deity, praying to different gods at different times. Commoners in a small town might visit a temple that has three altars, where they pray to Bahamut for protection, Pelor for fertile crops, and Moradin to aid their skill at crafting. Clerics and paladins more often serve a single deity, championing that gods particular cause in the world. Other adventurers range across the spectrum, from paying lip service to the whole pantheon, to fervently serving a single god, to ignoring the gods entirely as they pursue their own divine ascension.
Many deities have contradictory versions of how the world should work. Even the agents and worshipers of deities who share an alignment can come into conflict.