At work you have a few Linux servers and are asked to troubleshoot why a webserver on one of them is not responding. You SSH onto the server and want to determine if the webserver process is running. Which command would you use?
The ps command is a Linux and Mac command for listing processes. It is also an alias for Get-Process in PowerShell. The command will list running processes and various details about them. It is a great start to determine if something is running on a Linux machine.
Wikipedia
In most Unix and Unix-like operating systems, the ps program (short for "process status") displays the currently-running processes. A related Unix utility named top provides a real-time view of the running processes.