iPad and Air Video

In Air Video read here a paragraph: "Air Video works over local network and over internet (including 3G). However to enjoy streaming over internet your router must support UPnP or NAT-PMP protocols so that Air Video can setup the port forwarding for you. Otherwise you will need to configure the port forwarding manually".

Do I understand correctly that in this way, you can leave your home computer running Air Video Server then connects to the computer via the Internet from the iPad and then to watch movies on it.
Has anyone ever tried? I did not succeed, however, I have not yet set up the router like it says. I don't quite understand the mechanism how iPad find my computer.