Dqueue is a data structure that stores and retrieves elements based on the first in first out (FIFO) principle. It allows adding and removing elements from both ends with low overhead, making it efficient for handling data streams. There are three main types: linear queues with enqueues at the rear and dequeues at the front; circular queues where the front and rear positions are interchangeable; and priority queues that perform dequeues based on assigned element priorities. Dqueues can be used in emergency room triage, cloud computing load distribution, and food ordering systems to process items in received order. While allowing simultaneous enqueue and dequeue, dqueues' performance declines for non-linear use cases and larger lists due to increased memory usage.