What is a MAC address?

A Media Access Control address — a unique 48-bit hardware identifier burned into a NIC, used for delivery on the local network.

MAC = Media Access Control address

A unique 48-bit (6-byte) hardware identifier burned into every NIC.

* A 48-bit MAC splits into the manufacturer's OUI (first 3 bytes) and a device-specific identifier (last 3 bytes). *

Format: XX:XX:XX:XX:XX:XX (hexadecimal)

Example: 00:1A:2B:3C:4D:5E

Structure:

• First 3 bytes: OUI (Organizationally Unique Identifier) - identifies manufacturer
• Last 3 bytes: Device-specific identifier

Key facts:

• Layer 2 address
• Should be globally unique
• Used for local network delivery
• Also called "physical address" or "hardware address"

Memory tip: Expand it correctly — Media Access Control — it controls how a device accesses the shared physical medium.

Go deeper:

• MAC address (Wikipedia) — 48-bit hardware identifier, OUI + device id, burned into the NIC.
• Address Resolution Protocol (Practical Networking) — deepest on the "local delivery" angle: how MAC (hop-to-hop, L2) pairs with IP (end-to-end, L3) via ARP.