It's a service that stays between jellyfin and debris providers, kinda like what zurg and debridmediamanager does. It does lots of things, but mainly it'll let you use a single interface to add torrent in bulk to both realdebrid and torbox and have them show in a single folder. The archive will preserve all torrent it sees so you never lose them. It allows migrations from any provider so you can move infringing torrents to torbox. It downloads subs so that you don't need to rely on jellyfin which is terrible for that or need a other separate stack like prowlarr.

Jellyfin is also much less permissive than Plex about how you build your library, so it'll create a folder called curated/ with the videos organized so that jellyfin can pick them up.