Link-state is a type of routing protocol used in computer networks to determine the best path for data to travel. In this method, each router maintains a complete map of the network's topology, which includes information about all other routers and their connections. This allows routers to make informed decisions about the most efficient routes for data packets. When a change occurs in the network, such as a new router being added or a link failing, routers share their updated link-state information with all other routers. This process ensures that every router has the same view of the network, enabling them to quickly adapt to changes and maintain optimal routing paths.