A MAC Filter(Link Layer Filtering) is a filter manually added onto a router, that allows ONLY those specific MAC Addresses to access the router, thus the internet. To find the MAC Address on apple devices, go to settings, about, and it's under "WIFI Address" - "00-14-22-01-23-45" for example. Everything that has the need for an internet connection will have a MAC address, you just need to search for it.