What Is Pop Stack Item?

A stack is a last in, first out(LIFO) abstract data type and data structure. A stack can have any abstract data type as an element, but is characterized by only two fundamental operations, the push and the pop.
The push operation adds to the top of the list, hiding any items
already on the stack, or initializing the stack if it is empty. The pop
operation removes an item from the top of the list, and returns this
value to the caller. A pop either reveals previously concealed items,
or results in an empty list.