In Ethernet, different MAC addresses are used for Layer 2 unicast, broadcast, and multicast communications.
A unicast MAC address is the unique address used when a frame is sent from a single transmitting device to a single destination device.
In the example shown in the figure, a host with IP address 192.168.1.5 (source) requests a web page from the server at IP address 192.168.1.200. For a unicast packet to be sent and received, a destination IP address must be in the IP packet header. A corresponding destination MAC address must also be present in the Ethernet frame header. The IP address and MAC address combine to deliver data to one specific destination host.