What is the difference between a stack and a queue?

A stack is a Last-In-First-Out (LIFO) data structure, while a queue is a First-In-First-Out (FIFO) data structure.

In more detail, a stack is a linear data structure where elements are added and removed from the same end, known as the 'top'. This means that the last element added to the stack will be the first one to be removed, hence the term Last-In-First-Out (LIFO). This is similar to a stack of plates, where you can only add or remove plates from the top of the stack. In computer science, stacks are used in various applications such as parsing expressions, backtracking algorithms, and memory management.

On the other hand, a queue is another type of linear data structure, but elements are added at one end, known as the 'rear', and removed from the other end, known as the 'front'. This means that the first element added to the queue will be the first one to be removed, hence the term First-In-First-Out (FIFO). This is similar to a queue of people waiting in line, where people join the queue at the back and leave from the front. Queues are used in computer science in various applications such as scheduling processes in operating systems, handling requests in a web server, and in breadth-first search algorithms.

In terms of implementation, both stacks and queues can be implemented using arrays or linked lists. For a stack, the push operation is used to add elements to the top, and the pop operation is used to remove elements from the top. For a queue, the enqueue operation is used to add elements to the rear, and the dequeue operation is used to remove elements from the front.

In summary, while both stacks and queues are linear data structures, they differ in the order in which elements are added and removed. Stacks follow a LIFO policy, while queues follow a FIFO policy. This fundamental difference makes them suitable for different types of applications in computer science.