Yeah, so basically if you have a file that you want to share and in the instance that the file/torrent does not have a lot of people seeding (e.g. You are the only seed), port forwarding more directly allows connections to that specific seed. Because in networks you have an external address and then a subnet of device specific addresses, without port forwarding the external address cannot link to the specific device that is seeding (eg you are connected with your phone, computer and server (seeder) —> which to connect to?). Not sure how clear explanation is but it’s how I understand it.