MP3 - short for Moving Picture Experts Group (MPEG) layer 3 - is a compressed audio file format with loss of information (some frequencies are suppressed, stereo in the bass is lost).
This proprietary format was invented by
Fraunhofer-Gesellschaft and Philips.
It is generally used at a bitrate of 128 Kb/s (i.e. 16 KB/s), files are then 10 times smaller than the CD standard with still a quite good sound.
It is thus possible to listen to music on the web in realtime if your internet connexion is always above 128 Kb/s (with a 56K modem, it cannot work without a time of download).
Ogg Vorbis is also an audio compressed file format, slightly better than MP3 (like WMA, RealAudio, AAC or MP4 formats) and open-source, completely free.
