GIF (pronounced giff or jiff) is an image format that is quite common on the web--the acronym means Graphics Interchange Format. Most of the buttons on any web site are either GIFs or PNGs (pings). GIFs have a feature that allows them to loop endlessly and as such are a neat way to capture short bursts of successive images (sort of like a flip book). Images that take advantage of this feature are called "animated" GIFs. The effect can be mesmerizing.