The GIF file specification originated with the CompuServe online service. Its indexed-color format restricts it to a maximum of 256 shades, which limits its usefulness in reproducing continuous-tone ...
You can convert a JFIF file to JPG, though the two formats are nearly identical, and most software will open a JFIF file as a ...
While not a common way to manage images in OS X, converting images in the terminal is a quick and easy affair. You can actually use two different methods to convert image files using the command line.