Media Access Control(MAC) is a machine address that uniquely identifies each machine on the network. It uniquely defines the Network adapter/Ethernet card or what most people call the LAN card on a Local Area Network. MAC addresses are 12-digit hexadecimal numbers(48 bits in length), something like this 00:1C:EA:C2:63:25 It is quite unlikely that you will ever need to change your MAC/Physical address of your  computer, but it’s always better to know.