A program which runs another program, usually more visually appealing and sometimes with a better user interface. The term, which seems like a comes from describing a "front-end" and a "back-end" of something. In computers, the back-end is rarely seen, meant to be run in the background, out of sight. Front-ends are similar to plugins and skins.
A popular front-end is WinZip which handles ZIP files using a simple, command-line interface ZIP program but adds a windowing system with drag-and-drop capability. It also adds the ability to remove single files from a large archive, view individual files without unzipping the entire archive, and other features.