An acronym Joint Photographic Experts Group.

JPG or JPEG is a term for any graphic image file produced by using a JPEG standard.

A JPEG file is created by choosing from a range of compression qualities (actually, from one of a suite of compression algorithms).

When you create a JPEG or convert an image from another format to a JPEG, you are asked to specify the quality of image you want. Since the highest quality results in the largest file, you can make a trade-off between image quality and file size.