Multicast is a networking protocol that allows a single source to send data to multiple destinations simultaneously. In other words, it allows a single packet to be sent to multiple recipients at the same time, which is more efficient than sending a separate copy of the same packet to each recipient individually. This can be useful in a variety of situations, such as when sending video or audio streams to multiple devices on a network. Multicast is often used in IP networking, where it is supported by the Internet Protocol (IP) and allows for efficient distribution of data to a large number of recipients.