Pointer
Pointers point to something in the computer's memory. Everything stored in a computer is stored as a number, including pointers. A pointer is a number that  references another place in memory by its address.
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Pop
Popping is the operation of taking something off the top of a stack. Computers use pop operations to retrieve the stored return pointer and use it as a reference to get back to the original subroutine that made the call to the subroutine that just finished.

Program counter
Instructions are stored as a sequence of numbers in the computer just like anything else. The computer usually executes one instruction after another unless it is told to jump somewhere else. The program counter keeps track of what instruction in memory is being executed at any given time.

Push
Pushing is the operation of putting something new on the top of a stack. Computers use pushing to store the return pointer when one subroutine calls another subroutine.