CCNA Question:

Answer #1
The address for a device as it is identified at the Media Access Control (MAC) layer in the network architecture. MAC address is usually stored in ROM on the network adapter card and is unique.

Answer #2
The address used by MAC sublayer is known as MAC address. This address is known as permanent address of our pc it is hard coded in the NIC card. It s 48 bit address represented as 12 hexadecimal format. The address divided in to two part- OUI(organization unique identify) and EUI (extended user identify)