Duvet covers are a type of bedding, a soft flat bag that is traditionally filled with down or feathers, or a combination of both and used on a bed as a blanket. Duvets originally came out of rural Europe and were made of Eider, a type of duck's down, which is well known for its usefulness as an insulator. Duvet covers are still commonly used in Europe (especially in northern Europe and Scandinavia where it is the most common form of bed covering), and have become popular throughout the world in the late twentieth century.
Duvets reduce the complexity of making a bed, as it is a single cover instead of the combination of two sheets, blankets, and quilts or other bed covers, which is traditional in many parts of the world. Beds equipped with duvets are usually covered first with a flat or fitted bed sheet and then afterwards with a covered duvet. The cover is called a "duvet cover" or a "quilt cover" for obvious reasons.
Nowadays, a duvet is sometimes filled with wool or artificial fibers (such as polyester batting or other artificial materials). Duvet covers are also sometimes referred to as a comforter, although comforters are usually used for decorative reasons, while duvet covers are used for their warmth.