Dynamic Source Routing (DSR) is a protocol used in mobile ad hoc networks (MANETs) that enables devices to communicate without a fixed infrastructure. It allows nodes to dynamically discover and maintain routes to other nodes in the network, adapting to changes in topology as devices move. In DSR, each node maintains a route cache that stores the routes it has learned. When a node wants to send data, it checks its cache for a valid route. If none exists, it initiates a route discovery process, broadcasting a request to find a path to the destination, ensuring efficient communication in a constantly changing environment.