hey Op - I went through the same journey as you recently.
I found the exact same guide you linked - but here’s what I found on my journey from knowing literally nothing to having it work.
firstly that guide is a bit outdated and very terse, in fact most of the guides have at least one thing that’s outdated and several things not explained
Here were my learning steps:
getting confident with the Linux command line enough that “chmod” and “chown”, user:group, rm, nano, and other basic commands weren’t foreign to me
getting confident enough with docker and docker compose that I understand what a container, image, compose file are and how to both manipulate them and exec commands inside them
understanding the basics of what a VPN is and does so the terms proxy, reverse proxy, port forwarding, DNS aren’t alien to me
understanding the basics of Linux file management including dotfiles, fstab, mounting, blkid, and as mentioned chmod and chown
none of this is particularly hard to grasp once you’ve grasped it but most guides you see and people you meet along the way will assume all of the above is second nature to you. at first I would pull my hair out seeing suggestions like “have you shelled into the container to curl your public IP?” like what the fuck does that even mean
I started with VPN as thats the important protective part. I paid for Mullvad because its fairly cheap and stuck with it all the way. First I used their GUI app and then later I switched to Tailscale and ran it as an exit node.
I also found guides like YAMS (Yet Another Media Server), dockSTARTer, Trash Guides and the Servarr wiki and would jump between them, Uninstalling, reinstalling, going down paths that didn’t work and formatting my raspberry pi and starting from scratch several times. It took me about 6 weeks to skill up to the point where I’m confident knowing about all the parts of my setup.
I’m happy to answer all the questions I can (bear in mind I knew nothing about this a few months ago, but my newbie perspective could help because I know what it’s like to not really know what half these terms mean)
PS:to specifically answer "what do these tools do"
Ombi (optional) – allows other people (or yourself if you like) to select requests for things to download (tv shows and movies)
qBittorrent - the torrent download client, takes a torrent from Prowlarr (see next point) and downloads it to your storage
Unpackerr (optional) - if it happens to download as a rar or zip file, unzips it for you
Prowlarr (replaces Jackett) – takes requests from Ombi (optional part) or Radarr/Sonarr/Lidarr (usually de rigeur) and uses trackers to find torrents. Trackers are services that take “I am looking for this movie” and turn it into “here is the torrent”. Prowlarr is where you manage the Trackers
Radarr (movies), Sonarr (tv), Lidarr (music), Whisparr (porn), Mylar (comic books), and Readarr (books) are part Ombi (find me this movie) but when qBittorrent has finished downloading and Unpackerr has unzipped it, puts tv shows together into series/seasons, handles the meta data, organizes everything for you and talks to the other apps so your library isn’t just a /downloads/ folder full of random crap, also sometimes you’ll download episodes 1 and 2 from one source, 3 and 4 from another, Sonarr gives you a UI to group them all together.