A Stack is a fundamental linear data structure following the Last-In, First-Out (LIFO) principle. In this structure, the most recently added element is the first to be removed. Ideally visualized as a physical stack of plates, new items are placed on top, and items are retrieved from the top.
Stacks rely on two primary operations: push to add an element to the top, and pop to remove the top element. In computer programming, stacks are essential for managing memory and function calls. When a program calls a function, the system "pushes" data--such as the return address and local variables--onto the call stack. Upon completion, this data is "popped," returning control to the correct location. This mechanism ensures that nested processes are completed in the exact reverse order of their initiation.
In contrast, a Queue operates on a First-In, First-Out (FIFO) principle, processing data in the order of arrival.