They have a wiki which explains a lot: https://wiki.servarr.com/ as well as other arr software.
Edit: sonarr monitors your tv shows to make sure it has all episodes and grabs new ones. Radarr monitors your movie collection. It also connects directly to your torrent provider / seedbox. Can setup quality profiles and the like to customize which files get grabbed and what not. They also do bulk renaming of files to make sure plex sees them properly. Plus more.
How did I forget! here is him and his brother (orange boy is the one who was okay, gray white one is the one who almost died)