In this section, we will study MAC addresses. Each network card, whether it's a Wi-Fi card or a wired card, has a physical, static address, assigned by the card manufacturer. This is the Media Access Control (MAC) address. The MAC address is written on the card, and it's physical, so it never changes. It is used between devices, for identification and to transfer packets in the right direction. This works because each packet has a source MAC and a destination MAC, and travels from the source to the destination.
Because the MAC address is static and never changes, it can be used to trace back and identify a device. Also, since devices use MAC addresses to identify each other, we can have some networks that only allow certain MAC addresses to connect to them (by using a whitelist), or that blacklist MAC addresses so that they cannot connect to the network...
