Rilutaan: The Western Marches
The Feywild is a plane that is roughly adjacent to the world (cosmologically speaking) and is a reflection of it. However, the Feywild, sometimes also called Faerie, is a place of natural wonders and of natural extremes. Where a forest stands in the world, on the Feywild it may be a verdant, primeval forest that stretches for hundreds of miles. A mountain range may be extended and heightened to fantastic degrees. A cold bog becomes miles of treacherous swampland, inhabited by fearsome beasts.
This isn't to say that the Feywild is solely a dangerous place (though it is that), for there is beauty there also. The Feywild is home to many fey creatures, such as centaurs and dryads. Elves also can trace their ancestry back to the Feywild, in some of the longest-lived and well-documented elvish houses that still remain. There are other beings here as well, however: the eladrin. These creatures are similar to elves in appearance, but like other things in this plane, have a more exaggerated appearance: their ears are longer and more pronounced, coming to sharper points; their features are more angular and alien then are an elf's; and their personalities vary from extreme to extreme often, making them troublesome to deal with for mortals from outside the Feywild at times.
Many of the fey creatures are organized into courts, ruled over by the eladrin. These are the courts of Summer and Winter, also known as the Seelie and Unseelie fey respectively. There are whispers of other, more minor courts in the land and that bleed over into the wider world, but neither of the "official" courts recognizes these others.