Its one of the music sharing programs. Its relatively powerful, but since it is free to use, they sold out and made it full of adware and spyware (legal trojan horses). I've personally never used it.

If you actually want to download music off the internet, I'd recommend morpheus. Bear in mind that only about 1/4 of the songs downloaded off the internet are of decent quality. Most users simply don't care about their encoding.

-Biscuits