A duvet is a thick, warm blanket filled with down or feathers. Having a duvet on your bed keeps you warm at night.
Usually, a duvet consists of a puffy quilt — also called a "comforter" — inside a specially fitted cover. If you use a duvet and cover, you don't need a top sheet or a bedspread. Duvet is originally a French word, and it's retained its silent t in English, being pronounced "doo-vay." Originally the French word was dumay, a diminutive of dum, or "down."