Standard 8mm film is actually 16mm film split down the middle, so it can be exposed twice, thus giving consumers two times the footage for the same length of film. Like 16mm film, the reel comes loose and must be threaded into the camera. This can be time-consuming, especially when it's time to "flip" the reel and thread it the other direction to take advantage of the two sides. One of the main features of Super 8 is that it is sold in a cartridge that can be simply loaded into a Super 8 camera; no threading is necessary. However, this feature has the disadvantage, for advanced users, of not allowing for exposure tricks and special effects that can be achieved with an open reel.
Super 8 cartridges do allow for a small amount of rewinding on the projector, but not much of the film can be rewound before it piles up in the cartridge. There is another format called Single 8, which was invented by Fuji and popular mostly in Japan, that uses a similar cartridge system, but threads the film in such a way as to allow continuous rewinding.
The fastest way to know whether you're looking at regular 8mm or Super 8 is by examining the sprocket holes on the edge of the film strip. Because regular 8mm is derived from 16mm, the sprocket holes are larger and positioned at the top and bottom of each frame. Super 8 holes are smaller and positioned at the center of each frame.
Having smaller sprocket holes means Super 8 film has more room for image area than standard 8mm film. This means the film can capture more inside its frame. Super 8 frames are 5.46mm wide, while standard 8mm only dedicates 4.5mm of its area to the image. The idea of maximizing picture size on film stock was borrowed from Pathe, a French company that pioneered the idea of minimizing the edges, where the sprocket holes are, with its 9.5mm system in Europe.
The smaller sprocket holes also gave Super 8 a reputation for being a more stable film, since there is less wiggle room on the sprocket and, therefore, less tendency to jump around during filming. However, some film enthusiasts argue that the camera quality for consumer-grade Super 8 cameras negated this benefit, since the pressure plate holding the film in place was typically made of plastic instead of metal, providing a less firm spooling mechanism. Compared to the 8mm film cameras in use from the 1930s through the 1950s by consumers, though, Super 8 was a marked improvement on image stability.
While the cartridge containing Super 8 makes it easier to load and shoot with the camera, it presents an additional difficulty to those who prefer to process and develop their own film. Unlike loose reels of 8mm film, the cartridge must first be opened in a completely dark room in order to remove the film. This is usually done by gently cracking the case open with a hammer.