Open Shortest Path First (OSPF) is a routing protocol used in Internet Protocol (IP) networks to determine the best path for data packets. It operates within a single autonomous system and uses a link-state routing algorithm, which means it maintains a map of the network topology to make informed routing decisions. OSPF divides networks into areas to optimize performance and reduce routing table size. Each router shares information about its connections with other routers, allowing them to calculate the shortest path to each destination. This efficient method helps ensure reliable and fast data transmission across complex networks.