"is a digital hub connecting musicians — through collaboration we hope to forge a global society of musically talented individuals." - BandAmp.com
I think that summarizes it appropriately. BandAmp is pretty much everything2 except not quite everything and by that I mean limited only to original music.
The site, sort of like this one, provides musicians of all genres and expertise to connect and give feedback on posted songs. The site includes opportunities to showcase your music as well as participate in forums of all kinds and compete in monthly "battles", which are essentially competitions to accumulate the most votes for a song.
So if you're a musician looking to showcase yourself to the international musical community or just looking to hear some great original music check it out.