A training corset is generally a corset used in body modification. A training corset may be used for cosmetic reason (to achieve a smaller waistline, commonly called waist training or in more extreme cases tightlacing)
In addition, the term “training corset” may simply refer to a corset which is used to acclimate the body prior to wearing a full corset as an everyday underwear, or to any corset worn by somebody undertaking training (achieving a desired body shape).
These corsets are designed to be worn for long periods of time, e.g. overnight and during sleep.