Format name: GIF (Graphics Interchange Format)
Compression algorithm: LZW (lossless)
Color depth: up to 8 bits
Versions: gif87 and gif89
Released in: 1987
Gif file format is used to hold and transfer images in index color mode (not more than 256). The format also supports a lossless LZW compression algorithm (a single file may contain a set of images) and interlaced mode (interfaced image load).
In 1989 the format was updated. The name of the new version looks like gif89. It supports an additional channel to perform a transparency effect and to hold a set of images in a single file where frame show time and animation were displayed.
Nowadays the format is one of the most popular graphic formats. Though it not suited to hold a photorealistic images, for it cannot contain more than 256 colors. It is mostly used to display animation and drawing pictures without blend.
GIF format file has got a set of compression algorithm features that allows compressing images with sequential horizontal colors. That means that a file, which contains horizontal bars, will take fewer places than the same file with vertical bars.
Gif format, unlike Jpeg format, use a lossless compression algorithm. That means that while compression/decompression bits are not deleted. Gif uses a patent compression /decompression algorithm, which is called LZW (Lempel Zev Welch). Read more about the compression algorithm here.
Interlaced mode makes possible to refine images, as they are loaded. It is very convenient for big files, as you can see the main image features in several seconds after loading.