How do queues work?

Consider a pipe, perhaps a metal one in your bathroom or elsewhere in the house. Naturally, it has two open ends. Imagine that we have some elements in the pipe, and we're trying to get them out. There will be one end through which we have inserted the elements, and there's another end from which we're getting them out. As seen in the figure below, this is precisely how the queue data structure is shaped.

Unlike the stack data structure that we primarily think of with one "open end", the queue has two open ends: the front and rear. They have different purposes-- with the rear being the point of insertion and the front being that of removal. However, internally, the front and rear are treated as pointers. We'll learn more about them in the subsequent sections programmatically.

Note that the element that got inside first is the initial one to be serviced, and removed from the queue. Hence the name: First In First Out (FIFO).