MAC Addresses are unique for each Network Interface Controller (NIC) and most often are not configurable. Taking advantage of this fact in combination with the Organizationally Unique Identifier(OUI), many Network scanners use the MAC Address in order to determine the manufacturer of a Network Device or even the device type. As you can read in RFC 7042:
48-bit MAC "addresses" are the most commonly used Ethernet interface identifiers. Those that are globally unique are also called EUI-48 identifiers. An EUI-48 is structured into an initial 3-octet OUI and an additional 3 octets assigned by the OUI holder or into a larger initial prefix assigned to an organization and a shorter sequence of additional bits so as to add up to 48 bits in total.