A guest network is a second Wi-Fi name on the same home router or mesh system, with its own password. The idea is to let visitors, and some smart-home devices, reach the internet without handing them the password to everything else in the house.
What CISA recommends
CISA’s module on securing home Wi-Fi tells households to turn on the guest Wi-Fi option and to give it a long, unique password of its own. Guests who do not use your network all the time should be on that guest Wi-Fi, not on the main name your computers use.
The same guidance covers smart-home and other IoT devices — bulbs, plugs, cameras, speakers — when internet access is all they need. Put them on the guest Wi-Fi in that case. The point CISA states is to reduce their ability to discover other devices on your network or to reach the router’s settings. A gadget that only needs to talk to a cloud service does not need to sit next to your laptop on the main network.
What this page will not do
It will not list the taps inside the Google Home, eero, Orbi, Deco, or any other app. Those screens change, and a wrong click-path is worse than none. Look for a guest network, or a similarly named IoT network, in the app or the web page that manages your mesh system, and give it a different long password from the main network.
A guest network is not the same thing as WPA3. The password method is Wi-Fi security. The guest name is a separation on top of that. Use a current security mode on both names if the system lets you.
IoT radios that are not Wi-Fi
Some smart-home gear never joins Wi-Fi at all. Zigbee, Thread, and Z-Wave are other radios, with their own mesh behavior, used for sensors, bulbs, and locks. Matter is an application layer that can run over Wi-Fi or over Thread; it is not itself a Wi-Fi mesh kit. Those systems are easy to confuse with “mesh Wi-Fi” because the word mesh shows up in both. They are explained on broader wireless mesh, which is deliberately not a shopping page for home Wi-Fi systems.
If a device’s instructions say it needs your Wi-Fi password, it is a Wi-Fi device, and the guest-network idea above applies when it only needs the internet. If the instructions say Zigbee, Thread, or Z-Wave, it is not joining your Wi-Fi name, guest or otherwise.