Technical Jargon
http://www.videolan.org/
http://www.videolan.org/vlc/features.html
My Review
First, it plays any file, efficently. Two or more players can be used..like quick time.
Uses very less CPU Power unlike Media Player Classic,etc.
Good for high definition/high bandwith/high quality videos.
Highly customizable.(Skins/Outputs,etc.)
I've used Media Palyer Classic, Cyberlink PowerDVD 7, MP11, Media Center..
Nothing comes close to the effortless quality it provides.
I like to mention about PowerDVD the audio customization is better than VLC.