Figure 1 shows three ways of sending a message.  A woman is talking towards a group of people and is speaking only to one person in the group, this is a unicast.  When she speaks to more than one member of the group, but not the whole group she is sending a multicast message.  Lastly when she speaks to the group as a whole she is sending a broadcast message. Figure 2 shows a computer sending a message to a switch that has four other computers connected to it.  The unicast message is delivered to one specific host, the multicast message is delivered to two of the four computers, and the broadcast message is delivered to all of the other computers.