"All modern operating systems are able to run many programs at the same time. For example, a typical Linux server might include a Web server, an email server, and probably a database service. Each of these programs runs as a separate process. What do you do if one of your services stops working? Here are some handy command-line tools for managing processes.
"Each process uses time on a system's CPU, as well as other system resources such as memory and disk space. If a program goes wrong, it can start to use too much CPU time or memory and so deny other programs the resources they need to run..."
