Help with understanding Push/Pop and Enqueue/Dequeue

I have two different questions for each, Stack and Queue.

1) Variable S of type Stack. Add the value 12 to the stack S.

So, I believe the answer would be S.Push(12);

-What is the difference in S.Push(12) and Push(S,12)?

2) Variable S of type Stack. Removes top value from the stack S.

I believe the answer to be S.Pop();

- I am confused on whether it would be S.Pop() or Pop(S). What is the difference?

3)Variable Q of type CQueue. Adds value 'A' to the queue Q.

My answer is: Q.Enqueue('A').

- What is Enqueue(Q,'A')?

4) Variable Q of type CQueue. Removes value from queue Q storing it in the char variable C.

My answer: C=Q.Dequeue();

- I am little confused on this. What is C=Dequeue(Q)?