A duvet is a large flat bag filled with a highly insulating material, traditionally eiderdown. It is designed to go onto a bed, replacing layers of blankets, quilts, and comforters. Except in extremely cold regions, a single duvet is usually warm enough for sleepers, making it much easier to make a bed, and making that bed more comfortable to sleep in. The piece of bedding probably originated in Northern Europe, although it has since spread to the rest of the world.
The roots of the word can be found in the Old Norse dunn, for “down.” The word was picked up by the French, and slowly turned into “duvet” over several centuries of linguistic evolution. Since it is traditionally filled with down, the name is simple but descriptive.
In some countries, a duvet may be confused with a comforter, but there are some differences between the two. To begin with, a duvet is designed to be used with a cover. Down is very difficult to clean, and it is easier to simply bag a duvet in a washable cover that can be cleaned periodically. This bedding also tends to be flat, rather than puffy, since eiderdown, the traditional filling, is a highly efficient insulator, and it does not need to be used in large amounts. It's also a standalone piece of bedding, meant to be used with sheets only, and no other blankets or covers.
A comforter, on the other hand, often has no detachable cover. The entire piece of bedding can be washed, and it is often meant to be decorative as well as functional. The use of washable insulators in comforters makes them less efficient, resulting in the need for more insulation, creating a puffy appearance. Comforters are also usually used with blankets and multiple layers, which can be rather stifling in the opinion of some sleepers.
When selecting a duvet, one filled with eiderdown is the best choice, if it is available. Shoppers should look for bedding that is well sewn, since small holes can allow the filling to escape. A quilted duvet is also a good idea, since it ensures that the stuffing will not clump in one section. The color is not terribly important, since it should always be used with a removable covers. A wide range of covers are available in different patterns and colors for all tastes.