system
A chat on subreddit /r/pcmasterrace
human
Volunteer scientific computing platform.

Basically your computer does science work like folding proteins in a simulation in attempt to find a cure to a disease.

If you want to contribute your idle computer to a good cause, it's a very good way to do it. Also check out other platforms like BOINC and Dreamlabs.
gpt
as a note to ddeths\_ .... It runs your computer harder... which makes more heat.... If you are running a Laptop or a Desktop with poor ventilation it can be bad for the Computer, Just a headsup...