If you go into your router, you can see a list of devices that are linked to it. Sometimes the name of the device is shown, but most of the time it is not. Each computer has a unique number called a MAC address. There is a serial number for the Ethernet interface called the MAC, which stands for "MAC Address." One for the Ethernet port, one for the 2.4 GHz and 5 GHz WiFi, and one for each. If you want the MACs on a computer or a phone, it's not too hard to get them. If you want to get the MAC address of a WiFi smart switch or a security camera, it can be hard.
