You can think of instance and server as the same thing. An instance of lemmy runs on a server.
You don’t have to run an instance to create a community (sub), but I believe some instances limit who can create communities.
If you run your own instance, you could do whatever you please with it. When you create a community on it, other federated instances can browse to it via community@instance.domain
Here are the instructions for hosting your own instance
https://join-lemmy.org/docs/administration/administration.html
~~Is Threads federating? I thought it was just standalone. ~~
Searching around for “Threads Federation” or “Threads Fediverse” yielded nothing
Got it - ActivityPub was the term to use
Notably, Instagram head Adam Mosseri said in a post that there will be no ActivityPub support at launch. ActivityPub is — a protocol that is used to post on decentralized networks like Mastodon. But the platform plans to allow interactions with other fediverse servers in the future.
Nice, congratulations for completing a personal project. One day I also hope to complete a personal project.
What reference material did you use to build it? As in like the activitypub specification