JPG
1. To be exact, the name JPEG stands for Joint Photographic Experts Group, the name of the committee which created the standard of compressing photographic images .
2. However the term 'JPG' most often refers to a picture which was compressed using the JPEG standard.
Important facts to know about JPG compression:
JPG is a lossy means of compression. Using it more than once on an image will lead to blurry effects.
Example: You take a digital photo. You transfer the image to your PC. You crop the image and save it to disk. The next day you adjust the brightness of that image and save it to disk. The next day you adjust the colors of the image and save it to disk. The next day you adjust the levels of the image and save it to disk. Overall you have compressed and decompressed your image 4 times, the final result will have lost many details and will look blurry. In order to avoid this effect, perform all steps at once and save it once, or store the steps in a lossless format, such as TIFF or PSD.
