A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service . Multicast addressing can be used in the link layer (layer 2 in the OSI Model ), such as Ethernet multicast, and at the internet layer (layer 3 for OSI) for Internet Protocol Version 4 (IPv4) or Version 6 (IPv6) multicast.

Source: https://en.wikipedia.org/wiki/Multicast_address