Last.fm is a music engine based on a massive collection of Music Profiles. Each music profile belongs to one person, and describes their taste in music. Last.fm uses these music profiles to make personalized recommendations, match you up with people who like similar music, and generate custom radio stations for each person.

After picking a username and signing up, you would typically install an Audioscrobbler Plugin for your media player (iTunes, Winamp etc..) which sends the name of every song you play on your computer to Last.fm. Over time, this list of songs grows larger and larger - you can see your personal listening charts on your userpage. Last.fm automatically finds people with a similar taste, and generates music recommendations for you.