GIF = Graphics Interchange Format.  GIF is used to pack 8-bit images using [lossless compression].

GIF comes in two forms:

* GIF87, which is the normal format.
* GIF89a, which adds a single-color transparency.

GIF is quite obsolete by now, and while there are still plenty of GIFs around, you really should be using [PNG] as its replacement, since it offers much better compression, up to 48 bits colordepth, per-pixel transparency information, and all sorts of other goodies.