Basically it’s very similar to Flickr, but it’s sound related. You could download all kinds of sound effects, loops, single-shot instruments for samples and so on. And you could also upload your material, as long as you own the copyrights for that material.
Just read the fine print carefully, basically if someone else is using your material, you will not be compensated for this. Then again, it’s nice to be altruistic and give material for others, anyway. Usually, what I do with such sites is that if I use material from such sites, I also contribute, to keep the karmic balance, or even better, make it on the plus side.
One issue with similar sites is to maintain the quality, as the more its open, the more less quality material will be present at such sites. Then again, Flickr seems to work just fine, based on the tools there, so you could find really good quality material based on user feedback placed on entries.
We live in a really interesting post-modern world, where even high-quality sound samples are now available for everyone. It will most definitely increase the amount of music published, and I don’t think we are so far away any longer from the state where every consumer could make their own music — the truth is not so far away, already.