A queue is a linear data structure where the operations are operated in the FIFO (First in First out) order. The queue data structure is of 3 types: Circular Queue: The queue where there is no rear (i.e., the front is the rear itself), is called the circular queue. Dequeue: The queue that allows the insertion and deletion from both ends is a deque. Priority Queue: The queue where the element with higher priority is operated first is a priority queue. If two elements have the same priority, the one being higher in order in the queue will be served first. Some of the real-life examples of the queue data structure are: 1. Queues at the ATM. 2. CPU task scheduling. 3. Website request processing. 4. Input stream management system.