The name "leotard" was applied retroactively; Léotard apparently called the garment a "maillot".
Leotards are worn by acrobats, gymnasts, dancers and circus performers, as well as others. They are often worn together with tights.
Leotards have scoop necklines - entry is through the neck. (Compare bodysuit).
A leotard that is extended to include long legs, removing the need for tights, is known as a unitard.
Leotards can also be worn as lingerie and are eroticised by some people, often as part of a wider spandex fetishism.