Broadband says do I want to join a network on my network?

[Amtrid]

Can someone explain why my new WiFi hub is asking if I want to join another network on my network as this will make it faster.?

surely my network has one network and that’s that. 

“….has a separate network name on the same Wi-Fi network. Joining an additional network will improve your overall experience. Do you want to join "B…..”

is what it says 

[Mustrum]

@Amtrid   where are you seeing this message?

Which broadband service do you have, and which router model?