This file format for color-rich images was developed by the Joint Photographic Experts Group committee. JPEG compresses graphics of photographic color depth better than competing file formats like GIF, and it retains a high degree of color fidelity.
This makes JPEG files smaller and therefore quicker to download. You can choose how much to compress a JPEG file, but since it is a lossy format, the smaller you compress the file, the more color information will be lost. JPEG files can be viewed by a variety of downloadable software on both the PC and Mac.