Pandora is an Internet radio service that uses the Music Genome Project to find similar music to what a listener desires.
Once a song or band is selected in the Pandora interface, the site's software selects other songs and artists that are similar based on over 400 traits like tempo, key, gender of lead vocalist, level of distortion, type of background vocals and so on.
Although the service is free to listen (save visual and occasional audio commercials), you have a limited number of minutes you can listen in a month. In addition, only six skips per station are allowed per day. An additional $0.99 will allow for unlimited listening in a month. An upgraded service of $36 per year includes unlimited listening, no commercials, a dedicated music player, plus a higher audio bitrate of 192 kbps.
A competing service is called Slacker.
Many Internet connected devices like Blu-ray players and some TVs offer Pandora.