The first page in this group is called General.
Most users will find the available settings sufficient for setting up their WLAN. You can rename the access point, specify the number and width of the communication channel, select an encryption mode, etc. There are as many as 6 WPA encryption variants to choose from.
On the WPS page connection settings can be automatically transferred to the client via WPS technology. The RT-N15 allows doing that with a special button, but only in the Network Map.
On the Bridge page you can set the RT-N15 up for WDS mode (Wireless Distribution System) so that it would work with other WDS-mode access points to expand your WLAN coverage. However, for such a WLAN to be more or less secure, all of its constituents must be RT-N15.
To allow only specific clients to access the router, you should go to the Wireless MAC Filter page and enter the MAC addresses of such clients into the list.
The address, port and password of the RADIUS server that can be used by the RT-N15 for client authentication are specified on the RADIUS Setting page.
The Professional page contains the rest of WLAN settings most of which pertain to low-level parameters of wireless connection and should not be tinkered with in most cases. We guess the most demanded feature in this page is the schedule you can define for the router’s wireless access point.