MAC address
Each computer is given a MAC address by its computer maker. The way for giving MAC addresses to computers, created by Xerox, is used.  MAC addresses have 48-bits (how many 1s or 0s it has in it). As each of the twelve entries can have 16 possible values (0 through 9 and A through F), there are 1612 or 248 (or 281,474,976,710,656) possible MAC addresses. MAC addresses identify many things, such as the type of device being used.