When you use an Internet application or game, a request goes through a specific 'port' depending on its purpose. For example, HTTP or basic web browsing works through TCP port number 80 while sending emails works through TCP port number 25. Although you may have never heard of this concept before it is happening right as your viewing this site.
To prevent unauthorized traffic from passing from the outside world into your computer, a program or application called a 'Firewall' monitors all 65534 ports detecting any improper use. However, the Firewall does not know every good from bad message being sent and received and therefore can cause problems when using Internet application or games - thus, where PortWiki comes in handy. PortWiki will develop to have an index of all the TCP and UDP ports used by certain applications or games meaning network administrators or users can find out which ports they need to 'allow' in order to receive or send the proper information. This is known as Port Forwarding.
How Do I Port Forward?
Each router will most likely support Port Forwarding as these days it comes standard. Click on the Routers link underneath the Port Forwarding header on the left to view a list of manufacturer's that make routers and then choose a model from the manufacturer's category. The router profile should contain information about whether it supports port forwarding and how you can configure it.