A MAC (Media Access Control) address is a unique, hardware-based identifier assigned to network interfaces, such as Ethernet and Wi-Fi cards, for the purpose of identifying and addressing devices on a network. It is a 48-bit address typically represented as a string of 12 hexadecimal digits, separated by colons, such as "00:11:22:33:44:55".
Each device on a network has a unique MAC address that is used to identify it and allow it to communicate with other devices on the network. For example, when a device sends a packet of data to another device on a network, it will include the MAC address of the destination device in the packet so that the other devices on the network know where to send the data.
A device's MAC address is usually assigned by the manufacturer and is stored in the device's firmware. It is not typically user-configurable and is often referred to as the device's physical address.
Examples:
A laptop's Wi-Fi card might have a MAC address of "00:0A:E6:11:22:33"
A smartphone's Ethernet card might have a MAC address of "B8:27:EB:44:55:66"
Note: It is possible to change the MAC address of a device, a practice known as MAC spoofing, but it is generally not recommended as it can cause conflicts on the network and may violate the terms of service for some networks.