Multicast is group communication, from one-to-many or many-to-many users. This can be specified at the link layer (Ethernet), or otherwise.
Over IP, multicast can be done with IP (IPTV) or over UDP, where there are reliable multicast protocols like Real-Time Publish-Subscribe (RTPS) or Pragmatic General Multicast (PGM).
Unicast is one-to-one transmission – TCP and UDP are examples
Broadcasting is all to all networking, where each sender transmits messages to all receivers within a group.
Delivers a message to any one out of a group of nodes, that all have the same IP address shared by devices (like in NAT traversal). This is generally done through BGP.