Wikipedia Reference Information
A film format is a technical definition of a set of standard characteristics regarding image capture on photographic film, for either stills or movies. It can also apply to projected film, either slides or movies. The primary characteristic of a film format is its size and shape.
In the case of motion picture film, the format may also encompass audio parameters (though often not). Other characteristics usually include the film gauge, pulldown method, lens anamorphosis (or lack thereof), and film gate or projector aperture dimensions, all of which need to be defined for photography as well as projection, as they may differ.
The complete, up-to-date and editable article about Film Format can be found at Wikipedia: Film Format