Capsule summary on that: .WAV is raw uncompressed digital audio, while MP3 or Ogg Vorbis encode the raw sound data, dropping some minor details that the human ear overlooks anyway, in a way that results in typically from 10:1 to 20:1 compression. For a given file size, Ogg Vorbis sounds slightly better than MP3, plus Ogg is not subject to the Frauenhofer MPEG patents.
Re: Why "ogg" files...?