What is the main feature of a Stack data structure?

The main feature of a Stack data structure is that elements can only be added or removed from one end. This characteristic is known as Last In, First Out (LIFO), meaning that the last element added to the stack will be the first one to be removed. This structure operates similarly to a stack of plates; you can only add or remove the top plate without having to disturb the ones below it.

In practical terms, this means that operations such as push (adding an item) and pop (removing an item) exclusively affect the top of the stack. This design is particularly useful for scenarios like function call management in programming, where the most recent function call needs to be completed before returning to previous ones.

Other characteristics of stacks include the inability to access elements directly in the middle of the stack or maintain a sorted order, which distinguishes them from other data structures such as queues or arrays.