GIF (Graphics interchange Format)
A bit-map graphics file format.
GIF is limited to only 256 (8-bit) colors but is well suited to icons, logos, and simple animations where bright flat colors are desired. For complex animations Flash is superior.
A transparent GIF lets the background show through selected parts of an image so that images appear to float on the page. This is accomplished by using the same background color on the GIF image as the color of the background of the page it is placed on.
GIFs load quickly because of their limited color palette and it uses lossless compression so it does not degrade when re-sized.
See JPEG.