What is a mac address called?

Media Access Control address.

This is the hardware/vendor set address of a Network Interface Card. The format is xx:xx:xx:xx:xx:xx With the first 3 hexadecimal digits specifying the manufacturer.

Network routers and switches use this address to control traffic to a Network Interface card, it is often tied to a user assigned IP Address (b.b.b.b, 4 octets, usually decimal, 0-255 each).