Multicast routing is a method used in computer networks to efficiently send data from one source to multiple destinations simultaneously. Unlike unicast routing, which sends data to a single recipient, multicast routing allows a sender to transmit a single copy of data to a group of receivers, reducing bandwidth usage and improving network performance. To achieve this, multicast routing protocols, such as Protocol Independent Multicast (PIM) and Internet Group Management Protocol (IGMP), manage the distribution of data packets. These protocols help establish and maintain multicast group memberships, ensuring that only interested receivers receive the data, thus optimizing network resources.