MAC Address (Media Access Control address) is an identifier that uniquely identifies a host on your network. This unique identifier (MAC address) is used for tagging frames (a.k.a. data-packets or datagrams) associated with (originating from or being sent to) a host on a network. Simply put, the MAC address is a number that uniquely identifies a network device such as a Wireless Adapter, or an Ethernet card.

MAC addresses are sometimes referred to as Airport IDs (usually on Macintosh computers), Ethernet IDs, Hardware IDs, or Physical Addresses. MAC address are usually denoted using Hexadecimal codes -such as: bd:16:3e:c4:6a:df

Because MAC addresses are permanently recorded/assigned to a product by it's manufacturer, they are also known as burned-in addresses (BIA) or Universally Administered Addresses (UAA). However, considering that these BIA (or MAC Addresses) can be overridden with a Locally Administered Address LAA), they can be altered/faked.