JPEG or JPG for short is an image file format that stands for "Joint Photographic Experts Group", the name of the committee that developed it.  It is a very popular file type used by digital cameras and seen throughout the world wide web.  JPEG files use what is known as lossy compression, a method of reducing the size of the file while sacrificing some of the quality. While sacrificing image quality sounds like a bad idea, JPEG files can often apply a good amount of compression and reduction of the size of the file while maintaining very good image quality, and in some cases look almost identical to the original to the naked eye.  The reduction of file size make JPEG files ideal for posting on websites and sending via email.