What Is It?
What is Ogg Vorbis?
Ogg Vorbis is a new audio compression format. It is roughly comparable to other formats used to store and play digital music, such as MP3, VQF, AAC, and other digital audio formats. It is different from these other formats because it is completely free, open, and unpatented.
What do all the names mean?
Ogg
Ogg is the name of Xiph.org's container format for audio, video, and metadata.
Vorbis
Vorbis is the name of a specific audio compression scheme that's designed to be contained in Ogg. Note that other formats are capable of being embedded in Ogg such as FLAC and Speex.
Where do the names come from? What does the logo mean?
Xiph.org has a page explaining the sources and meanings of the names and logos.