Shapewear is lingerie designed to re-shape someone's body. It is most commonly a bra, a waist cincher, a pair of panties to uplift the buttocks, a pair of drawers to uplift the buttocks and shape the thighs, or a combination of these.
Shapewear is usually made of Lycra, and is so skin tight that it squeezes the body. It may have stiff strips to act like the bones of a corset. However, it is not normally as firm as a proper corset.
It resembles compression clothing, but has a different function and is not normally worn as outerwear.