JPG or JPEG is a bitmap format developed specifically for photographic images by the Joint Photographic Experts Group. It is best used for on-screen display or email exchange of large low-resolution photographs and other images with millions of colors and for temporary storage, such as on digital camera memory cards.
JPEG may look good on-screen and may produce nice inkjet prints, but it is not suitable for high resolution commercial printing. The relatively low file size of large JPEGs is achieved with a lossy compression scheme that tosses out bits of data — information about the image — each time it is edited and then saved. Images requiring editing should first be saved as TIFF or some other lossless format.