If you're online very much, sooner or later you're almost certain to run into graphics files. While there are a number of formats and "standards" currently in use, by far the two most common are the GIF and JPG file formats. (Incidentally, GIF and JPG are the file extensions for these two formats--that is, the 3 characters to the right of the period in the complete file name, such as SAMPLE.GIF or SAMPLE.JPG.)
GIF stands for "Graphics Image Format," or "Graphics Interchange Format." By far the most widely used format for digital graphics information, it achieved its popularity due to its use by the CompuServe Information Service. Most any kind of computer with any graphics capability at all will have some kind of software capable of displaying GIF pictures.
Recently, CompuServe has raised a storm of controversy by issuing threats of legal action against those who use GIF images without its consent (in spite of the fact that CompuServe does not own the format--it licensed it from its original developer). This, plus the development of newer graphics file formats which provide better picture quality and require less time to transfer between computers, has caused the GIF format's popularity to plummet dramatically.
At this writing, the format that seems to be coming most rapidly to the forefront is JPG, also known as JPEG. Developed by the Joint Photographic Experts Group, this format requires substantially less time to transfer between computers than GIF files. Like GIF, JPG file viewing and manipulation software is available for a wide range of computer systems. In fact, most Internet browser programs have both GIF and JPG support already built in.
There is an enormous number and variety of images available in both GIF and JPG formats. In spite of recent events mentioned above, neither format is liable to disappear any time soon.