MAC address means media access control address is a address of any network interface for communication. MAC addresses used in many network technology that also includes ethernet technology used in computer. MAC address generally stored in the ethernet adapter in its hardware. These days all the ethernet ports are on motherboard and the MAC address also stored on the motherboard of a computer.
MAC address is always unique throughout world and can work as IMEI address of mobile set. We can trace any computer using this address. With IP address we can search the location and with MAC address we can know the exact computer.