A queue is a linear data structure that follows the First In, First Out (FIFO) principle, which means that the first element added to the queue will be the first one to be removed, similar to a line of people waiting for service. Queues are used in various scenarios, including task scheduling, order processing, and breadth-first search in graph algorithms. The basic operations of a queue include 'enqueue' (adding an element to the rear) and 'dequeue' (removing an element from the front). Like stacks, queues can be implemented using arrays or linked lists, with both implementations allowing O(1) time complexity for enqueue and dequeue operations. One of the key differences between a queue and a stack is the order in which elements are removed. In a stack, the last element added is the first to be removed (LIFO), while in a queue, the first element added is the first to be removed (FIFO). This makes queues suitable for scenarios where order matters, such as managing tasks in a printer queue or handling requests in a server queue. Queues can also be classified into different types, such as circular queues, priority queues, and double-ended queues (deques). A circular queue is a linear queue that connects the last position back to the first position, allowing for more efficient space utilization. A priority queue is a specialized queue where each element has a priority, and elements are dequeued based on their priority rather than the order they were added. Understanding queues and their operations is essential for mastering data structures and algorithms, as they provide a foundation for many systems requiring order-based processing.