Heh..read the FAQ's, they tell you everything, but since you posted..
folding is basically a way you can donate your cpu to medical research..this program basically hammers away at 'protein folding' which is like running virtual experiments on human protein strands....i dont know a whole lot about the science,
however most people who overclock like it, i find it's a way to actually put your OC to use instead of just having an idle system ..
worldwide our teams about #60, if you join that could move up, and you can run multiple pc's under the same user-id and combine those points (you see your individual score + team score/ ranking, and worldwide ranking)
so when you arent using your cpu, you can run this and if you configure it to use maximum cpu it will just sit at 100% all night (another great way to test stability of your system)
if you read up and have any other questions we will try and help...we are starting a competition soon where you can win cpu's etc (there is a sticky in this forum) many people including myself are still looking for teams so if you are quick you could join one and maybe win yourself something...