Video Lan Client, or VLC, is a MediaPlayer and streaming server with support for many formats including DVD movies, DivX, and others, and runs on many platforms such as Linux, MicrosoftWindows, MacOSX, and more.
VLC is used by a number of third parties as well: eMule recommends it for previewing downloaded video, and Google Video uses a modified version of it.
At one point, the VideoLan? project made a separate server, the VideoLanServer?, but this is now deprecated in favour of using VLC as both client and server. Expansion of the VLC acronym is falling out of use, as "client" no longer describes the software.
VLC is hellish to compile, having dozens of dependencies, including libraries that are recommended to be staticly linked in (ie, from source, not -dev packages), and a non-standard install requires hand edited configuration. Installing the Debian package imports a lot of packages, including parts of X, but it is quite possible to run it without running X.