Ogg Vorbis is a completely open, patent-free, professional audio encoding and streaming technology with all the benefits of Open Source.
Ogg is the name of the container format for audio, video, and metadata by the Xiph.Org Foundation – a non-profit corporation dedicated to protecting the foundations of Internet multimedia from control by private interests. They support and develop free, open protocols and software to serve the public, developer and business markets.
Vorbis is the name of the audio compression (Codec) that’s designed to be contained in Ogg. There are other formats capable of being embedded in Ogg, these include FLAC (a Source Forge project) and Speex.