Vorbis is an open-source, patent-free audio compression specification created by the Xiph.org Foundation. It is part of Xiph's Ogg project to create a complete open-source multimedia format.
Vorbis is a compression method, not a file format. Vorbis streams must be encapsulated in a bitstream which provides framing and seeking capabilities. By far the most common bitstream is Ogg; however, in principle any encapsulation could be used. For example, it is possible to embed Vorbis streams in AVI files.
- Vorbis home page (xiph.org)