Port Forwarding
What is Port Forwarding?
Port forwarding or port mapping is a technique - which is widely used to redirect computer signals (ports) between LAN computers (Local network), and remote computers (Internet).
If your application supports Universal Plug and Play protocol (UPnP) / NAT-PMP option, then port forwarding is done automatically for you (UPnP is widely used on P2P applications, such as BitTorrent, uTorrent etc...). If your application does not support UPnP / NAT-PMP option, then you will have to manually configure port forwarding for such applications.
If port forwarding is too much of a trouble for you to set, then there is a solution for you as well. You can still make P2P applications, and all other applications work which require ports to be opened. Your just need to purchase Private IP add-on from Members page, and then set your computer (which will run torrent client) to Demilitarized Zone (DMZ) on your router.