Simple put, a duvet cover is essentially a fabric bag for a comforter. Sometimes referred to as a comforter (especially in the United States), a duvet is a type of bedding that is a soft flat bag filled with down, feathers, wool, or a synthetic alternative. It is protected with a removable cover, the duvet cover.It works almost exactly the way a pillowcase covers a pillow. The only difference: A duvet cover is typically closed with buttons, zippers, or ties.
Duvet covers do two Functions: First, they protect comforters from dust, sweat and dirt (this is important, because down comforters should only be washed every one to three years).
Second, as one of the largest visual elements in the bedroom, they serve as a key anchor for the room’s overall style—and, happily, one that’s easy to change when you’re ready for a new look.