A corset is a garment worn to hold and shape the torso into a desired shape for aesthetic or medical purposes (either for the duration of wearing this item, or with a more lasting effect). Both men and women are known to wear corsets, though women are more common wearers.

In recent years, the term “corset” has also been borrowed by the fashion industry to refer to tops which, to varying degrees, mimic the look of traditional corsets without actually acting as one.

While these modern corsets and corset tops often feature lacing and/or boning and generally mimic a historical style of corsets, they have very little if any effect on the shape of the wearer’s body.

Genuine corsets are usually made by a corset maker and should be fitted to the individual wearer. http://en.wikipedia.org/wiki/Corset

A corset dress (also known as hobble corset because it produces similar restrictive effects to a hobble skirt) is a long corset. It is like an ordinary corset, but it is long enough to cover the legs, partially or totally. It thus looks like a dress, hence the name.