GiF is a graphic file format. It can be a single layer or multiple layer document. Multiple layer documents can be animated. GiF's have the disadvantage of being limited to 256 colours. But are otherwise lossless as a general rule. However lossy filtering can be used (a little like jpeg quality) to lower the overall file size but also affect quality. Reducing colours used also helps reduce file size. GiFs are popularly used on the internet & is their main target destination.

There's various freeware, shareware & payable version programs out there that can create gifs. Try searching free gif programs. eg: http://www.google.com.au/search?hl=e...e+Search&meta=

The gifs I use on the forums generally have very limited colours ... perhaps as little as 4 or 16 colours & generally have lossy filters added to reduce the file size as much as possible with the view that as long as it is readable it is good enough. Reducing the file size is my main objective.