"ogg" is and audio media format. It is "GPL".
a "General Public License" For people of all
walks of life. The "ogg" audio format is used
on this website. You'll find that this particular
media format is a usefull and a good way to
listen to music, compress audio to a smaller
size and good for anything to do with audio.

You can find more information about "ogg"
at this link: http://www.vorbis.com/