Of the fairy realms, there are three:
Aeternum of the gods,
Avalon of the Seelie,
Pandemonium of the Unseelie.
Avalon, for the fae, is their realm of heaven. Here dwells the Summer Court and the good fairies. Beware making deals even with the good fairies, they will ensnare the unwary in their webs and bring them to their home to service the king.
Aeternum of the gods is the purgatory of the fae. The guardian sprites live within, closer to the human realm than the others. They will attend a summons for help, keeping the balance of nature as commanded by their creators.
Pandemonium is where the Unseelie live and where the Winter Court dwells. The fairy version of hell and where their devil reigns. The fae that live within are wicked and quick to anger, often declared outright evil, though much like demons there are shades of grey within this truth.
Artwork by @lamthetwickster