A deque, short for "double-ended queue," is a data structure that allows insertion and deletion of elements from both ends. This flexibility makes it useful for various applications, such as implementing queues and stacks. Deques can be implemented using arrays or linked lists, providing efficient access to both the front and back elements. In programming, many languages offer built-in support for deques, such as the collections.deque in Python. This allows developers to easily manage data that requires frequent additions and removals from either end, making deques a versatile choice for handling dynamic data sets.