A FIFO queue is a queue that operates on a first-in, first-out (FIFO) principle. First-in, first-out means that the request (like a customer in a store or a print job sent to a printer) is processed in the order in which it arrives. A first-come, first-served line is the most common type of queue that we join in our everyday lives and is generally accepted as the fairest way to operate a queue.
In queuing theory, the rule governing queue operation is known as queuing discipline. Besides first-in-first-out queues, other queuing disciplines include last-in-first-out, prioritized, and serve-in-random-order.
The online queues in Queue-it’s virtual waiting room are based on the first-in, first-out queuing discipline.