Stack is not a new container; it is a template adapter class. The adapter containers wrap an existing container and provide high-level functionalities. The stack adapter container offers stack operations while hiding the unnecessary functionalities that are irrelevant for a stack. The STL stack makes use of a deque container by default; however, we can instruct the stack to use any existing container that meets the requirement of the stack during the stack instantiation.

Deques, lists, and vectors meet the requirements of a stack adapter.

A stack operates on the Last In First Out (LIFO) philosophy.