Excerpt from Manual of the Planes published by Wizards of the Coast:
The Feywild (sometimes known as the Plane of Faerie) is a verdant, wild twin of the mortal realm. Towering forests sprawl for a thousand leagues. Perfect amber prairies roll between pristine mountain peaks soaring into the flawless clouds. Emerald, turquoise, and jade green seas crash along endless beaches. The skies are a perfect blue not seen in the mortal world—until storms come, coaldark thunderheads boiling with fierce winds and torrential rains. In this world, arcane power thrums through every tree and rock. All existence is magical.
The creatures native to the Feywild—the enigmatic eladrin, the vicious hags, the wild dryads, and the tyrannical fomorians—are all charged with the mystic energy of this plane. Some are blessed by it, and some are warped. Like the land around them, the fey who inhabit this plane run to extremes. Good fey are noble and just, protectors of the natural world and those mortals they choose to show favor to. Evil fey are dark instinct unleashed, all blood and claw and rage. The creatures of the Feywild can be kind, cruel, noble, monstrous, and savage—often all at the same time.