MAC Address
In plain terms
A unique hardware identifier for a network interface.
Going deeper
A MAC address is a factory-assigned identifier on a network card used for communication within a local network segment. It operates at the data-link layer.
Under the hood
Used by switches for local delivery (layer 2); unlike IPs, it doesn't route across networks.
Examples
Network cards, switches, local delivery, device identification, ARP.
Think of it like...
Like a device's permanent serial number used to find it on the local network.