ProcessViewer is a nifty, albeit rather dangerous, behind-the-scenes tool in Mac OS X. In UNIX (the operating system on which Mac OS X is built), applications and other things going on are called processes. Each application (and the OS itself) may run a number of processes at once. For example, if you open ProcessViewer, you may see a large number of processes running, even though you may have only one or two applications running.

Geeks and troubleshooters can use ProcessViewer to identify what processes are running, which user "owns" the process, and how much of the CPU and memory the process is using. You can even stop a process if you think it may be causing problems for you.

Messing around in ProcessViewer is not a good idea for most users. If you're having problems with an application, or with Mac OS X, try quitting open applications, force-quitting (Command+Option+Esc), or logging out and then logging back in again, before you start mucking around with processes.