It gives you and the users of your jellyfin instance a nice UI dashboard to search and request movies/series. The requests then get handed off to radarr/sonarr for downloading via your downloader (e.g. Sabnzb)

Instead of having to go into the less polished sonarr/radarr that would also expose some settings that you might not want other users to change, you get a nice dashboard. Similar to how you’d browse on a streaming site.

It shows you currently popular movies/shows and upcoming highly anticipated ones, you can search for a specific movie and when you click on it you get a helpful site. It displays all kinds of info similar to jellyfin, like cast, tags, relevant other movies, links to sites like rotten tomatoes or letterboxd, and so on. You can also search for persons and it’ll show you what they’ve been in/have produced. And when you want something you can easily request a download in your preferred quality setting.

You also may limit what and how requests from different users are handled.