A MAC address (Media Access Control address) is a unique identifier assigned to your network card. MAC addresses are most often assigned by the manufacturer of a network interface card (NIC), Now some networks implement and use MAC address filtering as a method of security.
Spoofing a MAC address can be used for multiple reasons, its real easy to spoof your MAC address in a windows operating system like windows 7.
https://en.wikipedia.org/wiki/MAC_address
https://www.technitium.com/
