Ogg

Being a Container format, ogg can embed third-party codecs (such as DivX, Dirac, XviD, mp3 and others) but usually Ogg is used with the following.

• Audio codecs
  • lossy
    • Speex handles voice data at low bitrates (~8-32 kbit/s/channel)
    • Vorbis handles general audio data at mid- to high-level bitrates (~16-256 kbit/s/channel)
  • lossless
    • FLAC handles archival and high fidelity audio data

• Text codec
  • Writ a text codec designed to embed subtitles or captions

• Video codecs
  • Theora based upon On2's VP3, it is targeted at competing with MPEG-4 video (i.e. DivX and XviD), RealVideo, or Windows Media Video.
  • Tarkin an experimental codec utilizing 3D wavelet transforms. It has been put on hold, with Theora becoming the main focus for video encoding.

(Taken from the wikipedia article)