the torrent file that you create, determines what data gets shared. a torrent file is just a checksum of data chunks. When you open the torrent file, you point it at your data (and hash check it) before sharing.
When downloading, you just point it at an empty directory with enough space and hope there are seeders đ
You certainly need to have your listening port open on your firewall if you want to have incoming connections, otherwise a connection will only happen if the other party opened their firewall correctly. it would work that way, but tends to not be wise if you are primarily wanting to be a seeder.
trackers are places that peers (the people with a given torrent file open) announce to, and the tracker helps them find each other, so that they can then connect directly to eachother. There is trackerless techm like DHT, but private trackers donât allow that. (the spleen). Magnet links depend on DHT technology. The Magnet link is just a checksum, so it can be embedded in the webpage and doesnât require a âdownloadâ like a .torrent file would. Then the torrent client uses DHT to find other peers based on that checksum. not an option on private trackers since they want to control who can connect.
https://www.lifewire.com/how-torrent-downloading-works-2483513
https://lifehacker.com/5875899/what-are-magnet-links-and-how-do-i-use-them-to-download-torrents