Port Forwarding is done within a router. It enables a machine to access certain applications that are pass through the router. By opening a port on the router, you are essentially punching a hole through the firewall. If you have downloaded an application or web service and cannot open it, there is a chance that port is closed on the router and you will either need to login and do port forwarding or contact the administrator of the network to do it for you.
Port triggering is a form of port forwarding. It allows a computer to make a connection to an outgoing server and when that reply comes back, the router then knows what computer on the network this connection belongs to.
Talk about port forwarding on our message boards
