Multicast - (1) "Multicasting" refers to the technology of sending the same message or content to a select group whereas "broadcasting" refers to sending the same message or content to everyone connected to a network, regardless of who wants to see or hear it.Multicast-enabled network - A network that has routers that can interpret Class D IP addresses.
To receive a multicast, a client must have access to a multicast-enabled network. In contrast, an unicast is a one-to-one connection in which one client receives a distinct stream from a server.
(2) Broadcasting TV programming via the Internet using broadband.
See the Interactive Television Institute.