How does port forwarding work

en.wikipedia.org/wiki/Port_forwarding

should use it for torrents

Well, if you have an Internet-accessible host that can listen on a port and another host that it can reach but isn’t directly accessible to the rest of the Internet that is running a BitTorrent client, it would allow the latter to accept incoming TCP connections.

You might have that scenario on a home network with a broadband router that’s Internet accessible and a connected computer with a private IP address.

IIRC, BT can operate without the ability to accept incoming connections, but if you can let it accept incoming connections, it’ll let you talk with other BT clients that can’t accept incoming connections, so you may get faster downloads and uploads.

tradeoffs

Depends on what else you’re considering. A dedicated Internet-accessible seedbox? Not having incoming connections?

If you are at home and your computer is connected to a router of some kind and the router in turn is connected to the internet, that is how you get access to the internet.

For something on the internet to connect to your computer you get a problem. You want this thing on the internet to connect to port X on your computer, but it can’t see your computer because the router is the one exposed to the internet. So the thing on the internet can connect to port X on the router… but you need it to end up on your computer.

This is where port forwarding comes in. It is a rule in your router saying “when something try to connect to port X, give it instead to <your computer> on port X”.

Edit to add: Note that in general you do not want random stuff on the internet to be able to do this. If you self-host something sensitive or personal, or just anything really, on this port, now an attacker can reach it. It may be password protected, or something more secure, but they are one step closer to getting to your computer.

When it commes to torrents, I think there is some part of DHT which needs some port forwarding. But I do not know the details.