What is PF usage in task manager ?

when i press Alt + ctrl + delete , a task manager come out ..... In the performance tab , there is CPU usage and PF history ... what is PF usage ? is that PF have any function in my pc ? Also , what is the difference between the CPU usage and PF usage ? is that PF usage means RAM usage ??? ANY pro or expert... show more when i press Alt + ctrl + delete , a task manager come out .....
In the performance tab , there is CPU usage and PF history ... what is PF usage ? is that PF have any function in my pc ?

Also , what is the difference between the CPU usage and PF usage ? is that PF usage means RAM usage ???
ANY pro or expert pls answer me ....tq ...
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