What does a MAC address uniquely identify?

A MAC address, or Media Access Control address, is a unique identifier assigned to network interfaces for communications on the physical network segment. This address operates at the data link layer of the OSI model and is used to ensure that data packets are sent to the correct device on a network. Since each device on a local area network (LAN) has a unique MAC address, it allows for precise identification of the device itself, rather than its location or the protocols in use.

The significance of the MAC address is primarily in the realm of local area networks where it plays a crucial role in network traffic management and device identification. Each MAC address is intended to be unique, as it is embedded in the hardware of the network interface card (NIC), further supporting its role in uniquely identifying devices on a network.