Dear,

Understanding of data structures is very important. Stacks, Queues, Linked Lists, Graphs are various Data Structures. Stack is kind of data structure which follows LIFO concept. LIFO basically means Last In First Out which means that the element that is added last into the stack will be popped out first. The elements are added from the beginning and deleted from the same end. A pile of books, a stack of dinner plates, a box of pringles potato chips can all be thought of examples of stacks. The basic operating principle is that last item you put in is first item you can take out. That is, that a stack is a Last In First Out (LIFO) structure.

Hope this helps!