what the hell is ogg? ogg vorbis is the open source standard for replacing the mp3 format. according to the developers it results in better quality and comes without commercial licenses or patent issues compared to mp3. to listen to that format you need a modern audio player. the following list of applications plays ogg files without a problem:
mac os x →
download the plugin from xiph, copy the xiphqt.component to ~/library/components/ and restart itunes.
download player or plugin - install - listen to the music