This link explains things fairly quickly for all debrid, the service I use is real debrid which you can follow identical steps for setting up: https://www.desidime.com/discussions/use-stremio-debrid-all-debrid-real-debrid-for-watching-content#:~:text=Debrid%20services%20are%20basically%20torrent,and%20windows%2C%20and%20works%20seamlessly.

The idea is essentially debrid services download the content of a torrent, and once one user has requested them, its stored and available for all other users to download, so no more dealing with Torrents with 0 seeders, at the speed of top grade file hosting services. You could use it for downloading content quicker and storing it on your local drives.