<<Ogg Vorbis is an audio-compression method comparable to mp3. It's key-difference when compared to mp3 is that it's 100% royalty and patent-free. Meaning: anyone can use it freely, without a need to pay Frauenhofer/Thomson Multimedia one penny. >>
MP3 is an open standard on format of a compressed music file. The method of accomplishing that compression is patented. This is why LAME generates MP3's royalty free, they wrote their own compression that is MP3 compliant and isn't based on Frauenhofer's work, and it only took them like 3 years to get something workable with quality that gets better every release.