jpeg is about the JPEG (Joint Photographic Experts Group) photographic file format. The JPEG format has become popular because of the capability to compress images and thus obtain high-resolution images at relatively moderate file sizes. The compression, however, involves loss of information and so when images are compressed down to a ration of 10:1 noticeable losses become apparent. JPEG is designed as a photographic format and is not well suited for line diagrams etc. with sharp contrasts since the compression algorithms may introduce artifacts.
latex is not able to import JPEG files unless they are embedded in an EPS file, while
lualatex can use them out of the box with the usual