From iA wiki
Full Title: MusicBrainz Community Music Metadatabase
MusicBrainz is a user-maintained community music database. Music metadata is information such as the name of an artist, the name of an album and list of tracks that appear on an album. MusicBrainz collects this information about music and makes it available to the public so that music players can retrieve information about the music that is playing.
For instance, an audio CD does not contain the name of the artist, album or a listing of the tracks. A music player can use the physical characteristics of an audio CD to lookup the correct metadata for the CD and show it to the user during playback.
MusicBrainz also takes this concept one step further in applying it to digital audio files like MP3 files and Ogg Vorbis files. The metadata contained in these files is often incorrect or missing altogether. If this data is not present or correct, it makes it difficult for users to find the music they wish to play. Many MP3 lovers have a huge collection of MP3 files but often have a hard time finding the music to which they want to listen. The MusicBrainz solution for this is the MusicBrainz Tagger, a Windows application that uses acoustic fingerprints (TRMs) to semiautomatically identify tracks in your music collection and then write clean and accurate metadata to your music files.
The MusicBrainz web site provides a catalog of music data that is known to MusicBrainz. Please understand that MusicBrainz only provides the data about the music and not the music itself. MusicBrainz does not condone copyright infringement and thus cannot help you find the best place to illegally download copyrighted works.
MusicBrainz users can browse and search this catalog to examine what music bands have published and how artists relate to each other to discover new music. The music metadata and its ability to uniquely identify music will also enable non-ambiguous communication about music, and will allow the Internet community to discover new music without any of the bias introduced by marketing departments of the recording industry.
Another important aspect of the web site is the creation and maintenance of the data. All of the data in MusicBrainz is user contributed and user maintained. This means that if a users spots a mistake in the database, the user should take the initiative to create a MusicBrainz account (for free of course!) and edit the data.
MusicBrainz asks that users contribute their knowledge about music and MusicBrainz will share their knowledge with others and in time MusicBrainz can become the most powerful and comprehensive music service in existence. In return for users' hard work, MusicBrainz makes the data that users have contributed available for download by the public. Some portions of the data are placed into the Public Domain, and some portions are covered by a Creative Commons license. For details, please take a look at the server/data product page.
This summary serves as the most basic crash course on what MusicBrainz does. The MusicBrainz project has many goals for the future with the hopes of changing how consumers enjoy their music collections. The detailed current status, the plans for the future, our views on working with commercial companies and our plans for creating a non-profit corporation are covered in great detail in our MusicBrainz Non-Profit White Paper.
http://www.shadetunes.com is a simple way to stay current on new music. It's an affiliate site for Apple iTunes.