graphics interchange format
Most color images and backgrounds on the Web are GIF files. This compact file format is ideal for graphics that use only a few colors, and it was once the most popular format for online color photos. However, GIF has lost ground to the JPEG format when it comes to photos. GIF images are limited to 256 colors, but JPEGs can contain up to 16 million colors--and they can look almost as good as a photograph.
CompuServe developed GIF in 1987, calling it GIF87, and two years later added new features such as interlacing, transparency, and animation to create the format known as GIF89a. People don't usually distinguish between the two GIF versions, so if someone refers to an image as a "GIF89" rather than simply a "GIF," it's probably animated.