"Using a music recommendation system called Audioscrobbler, Last.fm builds a detailed profile of each user's musical taste by recording details of all the songs the user listens to, either on the streamed radio stations or on the user's computer or some portable music devices. This information is transferred to Last.fm's database via a plugin installed into the user's music player. The profile data is then displayed on the user's profile page. The site offers numerous social networking features and can recommend and play artists similar to the user's favourites."
That's pretty much the main point, but if you want to read more, you can find information in last.fm or Wikipedia.
If you are interested, download that program and join the brand new EBT-group!

