I think of this like game servers.
The site you’re using is your platform (kbin=pc, mastodon=xbox, lemmy=ps). After that, the instances are what servers you connect to (lemmy.ca=psNA, whatever on mastodon=xboxSEA, kbin.social=pcEU. Then, federation is bringing it all together with crossplay.
Made a bit of sense to me, so hopefully this helps!
Some may call it heresy, but I abaolutely love thenes of old Windows on Linux. It’s familiar and nostalgic at the same time. Got a Windows XP theme on my Laptop, and plan to use a Windows 7 theme on my main rig when I finally set it up with Linux.