The MusicBrainz Tagger application allows you to automatically look up the tracks in your music collection and then write clean metadata tags (ID3 tags or Vorbis comment fields) to your files. As you tag the files in your collection that MusicBrainz didn't recognize, you submit the acoustic fingerprints (TRM ids) of your files back to the server. Submitting acoustic fingerprints will allow MusicBrainz to automatically identify these tracks in the future, so that other people using the Tagger can benefit from the work you have done.
As the community uses the Tagger application, more and more files will be automatically recognized. However, as we are just starting to collect the acoustic fingerprints, fewer files will be initially recognized. So, please download the Tagger and run your music collection through it so we can start collecting more acoustic fingerprints. You may also want to take a look at our statistics page to see how many TRM ids we've been collecting recently.