Okay, so I’ve been using Mastodon for years so I basically understand the idea of how content is propagated.

People on your instance are following someone and so you see the people they follow on your feed, or else they boost posts that they can see in which case people can see them on your feed.

I know this is using the same protocol but I’m trying to understand a few things –

It sounds like each instance has separate magazines, so this means different instances have different magazines. How does it handle it when two instances have magazines with the same topic? No real attempt at trying to merge the two? It seems impossible to do with distinct mods from separate servers with different rules, did someone figure out a way?

Similarly, if someone from @kbin.pub wants to comment on a thread in a magazine on @kbin.social or whatever (assume valid instances), how do they know that the thread exists? They subscribe to that magazine on a different instance and then see it in their own home page? Or does them subscribing to a magazine on another instance make that magazine appear to others on their own instance?

I guess I’m trying to understand how this system is handling discovery and moderation in a forum system where different instances split up a forum, it would be neat if things were somehow interleaved.

What terminology do I need to know?

This should suffice for now:
Fediverse: Basically a set of individual websites, the content of any one of which can be accessed through any other website from this set of websites. Read on for the ‘how?’
Magazine: Similar to a subreddit.
Thread: Similar to a Reddit post.
Microblog: Similar to a tweet on Twitter.
Post: A microblog posted in a magazine.

Find the navigation menu on kbin, which is at the top of the webpage if you are on PC or tap the trigram on the top left of the web page if you are on mobile. You should see items named ‘Threads’, ‘Microblog’, ‘People’ and ‘Magazines’ in the navigation bar.

How do I subscribe/join/whatever a community?

To browse the list of all magazines or search for specific ones, simply click on ‘Magazines’ on the navigation bar. When you do, you’ll find a search bar to search for magazines and a list of magazines sorted by the most number of subscribers. You can search for a magazine by just typing in a keyword like ‘history’. The search results will bring you magazines from kbin that have the keyword ‘history’ in their names or descriptions. In addition to kbin magazines, you will also find communities from other sites of the fediverse.

Here are the first 5 results I get searching for ‘history’ in the magazine search:

• chess
• Etymology
• historymemes@lemmy.ml
• history
• askhistorians@lemmygrad.ml

The magazines of kbin appear with just their name, as in the case of the chess, Etymology and history magazines. The communities analogous to kbin magazines on another fediverse site, lemmy.ml appear as you see in the case of historymemes@lemmy.ml. lemmy.ml is a different website from kbin.social, but you can access and interact with the content from lemmy.ml through kbin.social and using your kbin.social account. Click on the magazine name and you’ll find the option to subscribe on the right side of your screen on PC. On mobile, scroll all the way to the bottom and start scrolling up and you should find it. You can access your feed with content from subscribed magazines by clicking on the list icon to the left of your username on the top right of the web page on both PC and mobile. A dropdown menu will open up with an item called ‘Subscribed’. There you go.

I guess this might post to other websites as well?

You have posted to kbin.social in the RedditMigration magazine. A user of some other fediverse site will only see it if they are browsing RedditMigration@kbin.social from their site. If a user from some other website engages with your post, their user ID will appear here as username@fediversesitename, similar to how yours is username@kbin.social.

How do the points work (agree/disagree, relevant/not relevant, something else…)?

Favorite(up arrow)/Reduce(down arrow). Who favorites/reduces a particular thread/comment is public. Find the ‘more’ option on a comment and click on ‘activity’.

Another form of engagement is boosting (find the ‘boost’ option near the ‘reply’ option on a thread/comment/microblog), which is similar to retweeting on Twitter.

Is there a good overview somewhere?

An overview of fediverse can be found at jointhefediverse.net.