weave@angledweb

Ogg is a patent-free, fully open multimedia bitstream container format designed for efficient streaming and file compression (storage). This means that it can hold different types of media, dealt with by different codecs; so a ".ogg" file could refer to, say a video or an audio stream of data. Most often, "ogg" refers to the audio file format: Ogg Vorbis. This is a Vorbis-encoded audio in an Ogg container.

More can be read, by way of explanation, on Wikipedia: http://en.wikipedia.org/wiki/Ogg.

If you want a client to play Ogg Vorbis files, take a look at http://vorbis.com/software/.