In the beginning of the motion picture era, most films were shot in the 35mm format--indeed, this holds true to this very day. However in the 1920s, a new format, 16mm, came on the scene that was less expensive and used less bulky equipment. This format was quickly adopted as the format of choice for lower-budget independent movies. It also became the standard for television programs and news-gathering services.
The 8mm format was a natural evolution from the development of the 16mm format, reducing the costs and equipment bulk even further. This development put movie recorders directly into the hands of the average person and saw the explosion of the home movie.
The 8mm format is represented by standard 8mm and Super 8mm. The Super 8mm category is further split into several different classes of Super 8mm, so you want to be certain that what you are buying is what your equipment supports. Though the availability of film stocks and processing facilities has dwindled in recent years, 8mm is still a viable format for many purposes.
Oliver Stone has used super 8mm film in blockbusters like JFK and The Doors. You can also find many low- and no-budget films from student and independent filmmakers in the 8mm and Super 8mm formats.