Definition - What does Multicast mean?
Multicast is a communication method and data delivery scheme in which a single source sends the same data to multiple receivers simultaneously. It is similar to broadcasting but more secure because it has an added bonus of receiver discretion, where the data is received by specific users or hosts.
Techopedia explains Multicast
The multicast process involves a single sender and multiple receivers. versus systems that are designed to be connection-dependent, like a client-server system. User datagram protocol (UDP) is the most common protocol used with multicasting.
Email is the best example of multicast, where a user can choose to send mail to many different addresses, rather than a complete contact list. Another example is the one-to-many multicasting of a streaming video toward many users from a single server. Another good example is Internet protocol (IP) multicasting, where network nodes, like switches and routers, handle data packet replication through multicast groups.
Non-IP based multicast implementations include Internet Relay Chat (IRC), which is well scaled for large numbers of small groups.