The answer is Service Set Identifier or SSID.
Every wireless router sends out a beacon signal to allow other devices such as laptops, wifi printers, personal cellphones when set to look for and connect to the routers SSID. This SSID can also be shut off or hidden from public domains so not every person stopping by can try to connect to the router via the SSID. Usually you must have a password to follow an attempt to connect to the exact wireless router.