From Oleg Kovalenko:
Windows is a multitasking system. It means that a lot of various applications are running simultaneously in it. You directly work with some of them, but some of them work invisibly and independently. The priority of an application is a parameter that tells the system which task has priority over other tasks. If you have some database service running on your computer, it is useful to set a lower priority for it so that it does not interfere with the work of those applications you are using at the moment. You can change the priority of processes on the Processes tab of Task Manager. Prio automatically detects any changes in priority and saves them in its settings. Next time you start this application, its priority will be restored.