Bustiers - a bustier is traditionally worn as lingerie and considered to be form fitting. It reaches down only to the ribs or the waist and its primary function is to push up the bust by tightening against the upper midriff and forcing the breasts to move up, at the same time shaping the waist. Nowadays, bustiers are often made with mesh panels instead of boning. Bustiers can double up as a push-up bra for inner wear or as a camisole for outer wear.
Corsets - a corset's primary function is to shape and mold the torso. Both men and women are known to wear corsets to shape and slim their upper body. These days a corset is not technically a corset in the traditional sense. Modern corsets often feature lacing and/or boning and resemble the historical style of corsets, but they have very little if any effect on the shape of the person's body. The fashion industry mimics the look of traditional corsets without actually acting as one. Genuine corsets are usually made by a corsetmaker and should ideally be fitted for the wearer.