In computer science, a stack is an abstract data type that serves

as a collection of elements, with two principal operations:

* **push**, which adds an element to the collection, and

* **pop**, which removes the most recently added element that was not yet removed.

The order in which elements come off a stack gives rise to its

alternative name, LIFO (last in, first out). Additionally, a

peek operation may give access to the top without modifying

the stack. The name "stack" for this type of structure comes

from the analogy to a set of physical items stacked on top of

each other, which makes it easy to take an item off the top

of the stack, while getting to an item deeper in the stack

may require taking off multiple other items first

Simple representation of a stack runtime with push and pop operations.


[Wikipedia](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))