From the site:
Free Napster"You can search our catalog of 3 million songs and stream songs up to 3 times each for FREE. After the 3rd free play of any single track, you can either purchase the track or become a Napster subscriber. As a subscriber, you can download an unlimited number of full-length songs to your PC. As a Napster To Go subscriber you can transfer those tracks to your compatible portable player without paying per track."