The small, compressed format is what made them ideal for transmission over telephone modem lines - specifically what they were designed for. GIF images cannot exceed 256 colors. It was created when most home computer users had IBM compatible PCs which were capable of only 256 colors at the time. Until recently GIF was the format of choice. There are a few types or varieties of the GIF format.
All types are capable of being viewed by internet web browsers.
GIF is a multiple-image format, capable of simple animation. The 89a GIF format is capable of transparency. GIF has been the subject of much debate and controversy because the compression format it uses is patented. Commercial programs using GIF formats now have to pay fees for its use. Quite simply, JPEG was created to provide the best compression possible for highly detailed images.