Explain the main differences between push and pop commands when working with a stack.

The push and pop commands are basic operations for working with a stack (a LIFO data structure — Last In, First Out).

• push — adds an element to the top of the stack.
• pop — removes and returns the element from the top of the stack.

Example:

If the stack contains elements [1, 2, 3] (3 is the top), then after push(4) the stack becomes [1, 2, 3, 4]. After pop() the 4 will be removed, and the stack will revert to [1, 2, 3].

Thus, push increases the size of the stack, and pop decreases it and returns the last added element.