PIC micro controller oscillator frequency
(1) What I believe it says, is that 1 instruction cycle (machine cycle) takes 4 oscillator cycles to complete.

(2) The oscillator cycle is the time taken for a complete revolution to occur, or to put it simply, the time it takes to go from low, to high and back to low. The oscillator frequency is how often this cycle will occur every second, so 4MHz will mean 4 million cycles per second.

(3) The machine cycle or instruction cycle consist of 4 Q cycles. These Q cycles are what you would have shown us above.
The pic18 family manual that I’m using explains it better than I could. Try giving this a read to see if you understand.


And this


If you’re still confused about it, try to pinpoint where you got confused :) and I’m sure someone will be able to explain it to you in a way you’d easily get the concept.