Well for those in the (don't)know, GIF means Graphic Interchange Format (also known as a lossless format, because little detail is sacrified in the compression process), JPEG stands for Joint Photographic Experts Group (often used for photographs and sacrifices a little more detail). BMP stands for Bitmap. TIFF is short for Tag Image File Format (oh ... Jun didn't mentioned that one). PNG ... forgot that one.
The real question is how the "founder" pronounced "GIF" ... we won't go there.