Folding @ Home is using are computers to answer really hard math problems to help simulate how cancers are formed in the human body. When F@H first started it would have taken 30 years for 1 PC to answer 1 question but if they break up the question into smaller pieces they can send all the pieces out at once to everyone and have them solved and returned in a short time and put back together and have the overall answer in a few Days/Months/years.
So basically all are PC's are working together to make the Biggest supercomputer in the world and it's working to cure cancer
