A circular queue is a data structure that extends a normal queue by connecting the last element of the queue to the first element, forming a circle. This structure is also known as a "ring buffer". The operations on a circular queue are performed based on the FIFO (First In First Out) principle.

In a normal queue, we can insert elements until the queue becomes full. But once the queue becomes full, we cannot insert the next element even if there is space in front of the queue. In contrast, a circular queue can utilize the unused memory locations in the case of ordinary queues.

The following are the operations that can be performed on a circular queue:

• Enqueue: add an element to the rear of the queue
• Dequeue: remove an element from the front of the queue
• Front: get the front item from the queue
• Rear: get the last item from the queue

Circular queues can be implemented using arrays or linked lists. In array-based implementation, the circular behavior is achieved by manipulating the queue pointers. In linked list-based implementation, the front and rear pointers are used to manage the linked list, ensuring a circular structure.

Circular queues have several applications, including memory management and computer-controlled traffic systems.