A queue is a type of list where data are inserted at the end and are removed from the front. Queues are used to store data in the order in which they occur, as opposed to a stack, in which the last piece of data entered is the first element used for processing. Think of a queue like the line at your bank, where the first person into the line is the first person served, and as more customers enter a line, they wait in the back until it is their turn to be served.
A queue is an example of a first-in, first-out (FIFO) data structure.
A double ended queue also called as deque is a list in which the elements can be inserted or deleted at either end in constant time. It is also known as a head-tail linked list because elements can be added to or removed from either the front (head) or the back (tail) end. However, no element can be added and deleted from the middle. In a deque, two pointers are maintained, LEFT and RIGHT, which point to either end of the deque.