This is example of a HTTP based Wi-Fi credential configuration web service.
By default, the board creates an Access Point and starts a server which provides this web interface.
This interface shows you nearby available Wi-Fi networks. Clicking on the one you would like to connect to allows you to enter the credentials. The board will then switch to client mode and attempt to connect to it.
If connection is successful, the credentials are stored in board flash memory so that next time the board starts up, it connects directly to the configured Wi-Fi network.