The physical address, also known as the link address, is the address of a node as defined by its LAN or WAN. It is included in the frame used by the data link layer. It is the lowest-level address. The physical addresses have authority over the link (LAN or WAN).
Ethernet uses a 6-byte (48-bit) physical address that is imprinted on the Network interface card LocalTalk (Apple), however, has a 1-byte dynamic address that changes each time the station comes up.
Most local area networks use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown below:
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address or MAC address.
Physical addresses can be either unicast (one single recipient), multicast (a group of recipients), or broadcast (to be received by all systems in the network).
Checks Types of casting here.