It just means your router does not broadcast its SSID (basically its address and name) to other potential connections. You will need to connect to it using its IP address and use a passphrase key to secure the connection.
He’s not talking about his router. He’s talking about a router that shows up in his router list.
Somebody is probably pranking him.
I saw a router named “FBI_VAN” in my list once.
I have a spare router connected to nothing that I left powered up as “MAGA.”