A non-linear editing system is a video editing or audio editing system that can perform random access on the source material.
The very earliest non-linear film and video editors used laserdisc storage, but were quickly superseded by editing systems that used computer disk storage and compressed video.
The first two computer software based systems were Lightworks and Avid, and they forever changed the way that films and TV programmes were edited. Both systems used custom hardware for video processing.
With the availability of commodity video processing hardware, many software packages are now available for non-linear digital video editing, including:
- Adobe Systems Premiere Pro 
- Avid XPress Pro  (realtime)
- Discreet edit
- Apple Computer Final Cut Express/Pro 
- Media 100
- Cinelerra (free software) 
- Kino for Linux
- VirtualDub (free, GPL video software for Microsoft Windows)
- VirtualDubMod (VirtualDub with lots of added formats and features)