Dynamic Source Routing (DSR) is a protocol used in mobile ad hoc networks to facilitate communication between nodes without the need for a fixed infrastructure. It allows nodes to dynamically discover and maintain routes to other nodes in the network, adapting to changes such as node movement or network topology alterations. In DSR, each node maintains a route cache that stores the routes it has learned. When a node wants to send data, it can use the cached routes or initiate a route discovery process to find a new path. This flexibility makes DSR efficient for environments where traditional routing methods may fail due to mobility or frequent changes in network structure.