The document discusses stacks and queues, which are common data structures that follow the Last In First Out (LIFO) and First In First Out (FIO) principles respectively. Stacks allow insertion and deletion of elements from one end only, while queues allow insertion from one end and deletion from the other end. Circular queues are better than linear queues as they make more efficient use of memory space by allowing insertion at the start when the end is reached. Multiple stacks and queues also allow managing multiple such data structures.