This menu option will bring up the port mappings window, where you can add, edit and remove port mappings.
A port mapping allows an incoming TCP or UDP connection on a certain port on your mobile device (the Local Port) to be forwarded to a Destination IP and Port of one of the devices you have connected to the internet through WMWifiRouter.
When setting this up, it is important to know that for this to work you need to use a port that is not blocked by your provider (many cell providers block commonly used ports). Even then it may be the case that your mobile device is not connected directly to the internet, but behind another NAT proxy on your provider's network.
Note that this option has no effect on some combinations of devices, ICS and Windows Mobile versions.