The Stack is a fundamental linear data structure that follows the principle of Last-In, First-Out (LIFO). This means that the last element added to the stack will be the first one to be removed. It is analogous to a stack of plates: you add a new plate to the top, and when you need a plate, you also take one from the top.
A stack has two primary operations: push, which adds an element to the top of the stack, and pop, which removes the element from the top of the stack. Stacks are used extensively in computer programming. One of the most important uses is for managing function calls. When a program calls a function, the system "pushes" information onto the call stack, including the return address (where to resume execution after the function finishes) and the function's local variables. If that function then calls another function, more information is pushed onto the top of the stack. When a function finishes, its information is "popped" off the stack, and execution returns to the address that is now at the top. This LIFO structure ensures that functions are exited in the reverse order that they were called.
The opposite of a stack is a queue, which operates on a First-In, First-Out (FIFO) principle.