Function
Folding@home when running takes advantage of unused CPU cycles on a computer system as shown by this computer's 99% CPU usage.Folding@home does not rely on powerful supercomputers for its data processing; instead, the primary contributors to the Folding@home project are many hundreds of thousands of personal computer users who have installed a client program. The client runs in the background, utilizing otherwise unused CPU power. The older, no longer used version of Folding@home for the CPU could be run as a screen saver, only folding while the user is away. In most modern personal computers, the CPU is rarely used to its full capacity at all times; the Folding@home client takes advantage of this unused processing power.
The Folding@home client periodically connects to a server to retrieve "work units", which are packets of data upon which to perform calculations. Each completed work unit is then sent back to the server. As data integrity is a major concern for all distributed computing projects, all work units are validated through the use of a 2048 bit digital signature.
Contributors to Folding@home may have user names used to keep track of their contributions. Each user may be running the client on one or more CPUs; for example, a user with two computers could run the client on both of them. Users may also contribute under one or more team names; many different users may join together to form a team. Contributors are assigned a score indicating the number and difficulty of completed work units. Rankings and other statistics are posted to the Folding@home website.
when your computer is not in use you use the client and it uses your not CPU and you help research and do work for them
http://en.wikipedia.org/wiki/Folding@home