The settings of the WAN category refer to the WAN port parameters. First goes the Internet Connection page where you can choose the type of connection with the external network and set up its parameters. You can also direct streaming traffic to a dedicated LAN port (which can be very useful, for example, for IP television).
The router’s QoS rules are specified on the QoS page. Unfortunately, there are few options here and, judging by some settings, the rules only apply to uplink traffic.
Port triggering rules are specified on the Port Trigger page. There are but two ready-made rules here.
For some servers on the LAN to be accessible from the WAN, you should write appropriate rules on the Virtual Server page. As opposed to the previous page, there is a long list of predefined rules here.
On the DMZ page you can send all incoming traffic to a specific machine on the LAN.
Your DDNS account parameters are specified on the DDNS page. There are four DDNS providers to choose from, like on most other home routers.