A WPS button refers to a Wi-Fi Protected Setup button. This is a button on a wireless router that makes it easier to connect to the router.
For a WPS to work, the user must input an eight-digit numerical pin to access the router. This is not always secure, because the router only checks the first four digits, rather than all eight digits at once, making the router vulnerable to hackers. A secondary, slightly more secure way to implement WPS is with a button on the router. When the user pushes the button, someone can connect to the router without a password. The physical access required to connect makes this method more secure.