Editing & Post-Production
Non-linear editor
Also called: NLE, editing software, editor app
The name is a leftover from tape, where editing meant copying shots in order and changing one meant redoing everything after it. A non-linear editor leaves the source files untouched and stores your decisions as a list, so any clip can be replaced or shifted at any point without disturbing the rest.
Everything else follows from that: multiple video and audio tracks, undo, project files holding no media themselves, proxies standing in for large files. It also means the project depends on media staying where you left it, and offline clips are the most common panic in an editor's first month.