PF means page file & Cpu means processor. If u want to know about page files then, u should be familiar with RAM & how it works. RAM is basically a memory which contains some memory about ranning programs and recently used programs. Just like if u are working with 2 or 3 applications e.g. u are browsing 3 or 4 sites at one time, u click on the other application to work on that, application is ready for ur work, the memory that u are working on those file are stored in RAM. its not permanent memory. But for temopary use, And the files being used are kept in the manner is called page files. so pf usage, u can calculate usage of RAM. now cpu usage, the graph in that area shows how much work or load is being pressured on ur processor. If it is 100%, then system would be slow, because all the efficiency is being used by cpu.