A mezzanine floor is an intermediate level or partial floor that is built between the main floors of a building, typically in a space with high ceilings. It is often used to maximize floor space by adding an additional level without constructing a full floor. Mezzanines are commonly found in commercial, industrial, and retail buildings, and they serve various functions such as extra office space, storage, or viewing areas. They are usually not fully enclosed and are accessible by stairs.