I signed up for a couple of Fediverse instances that interested me; Lemmy, Mastodon, and Mbin. The app I use on my phone for Mbin is called “Intersteller”. When I filter by “all” posts on Intersteller, it shows Lemmy posts as well. Are they the same instance? If not, why is it showing Lemmy posts?


Welcome!
We have some guides / infographics for new users, which you might find helpful. These two pages in particular:
https://fedecan.ca/en/guide/get-started
https://fedecan.ca/en/guide/threadiverse/detailed-overview
An instance is the site where you make an account. If we extend the analogy to email, then
gmail.comis one instance whilehotmail.comis another instance. If you make an account on Gmail, you can’t use that login on Hotmail but you can still see content from people on Hotmail.Lemmy, Piefed, Mbin, Mastodon, Pixelfed, etc. are all software. It’s hard to extend this analogy out, but imagine if Google released the code for Gmail freely so that anyone could easily set up an email website that had the same appearance and functionality as Gmail. That is what is happening here.
So in the same way,
lemmy.ca,lemmy.world,sh.itjust.worksand many other Fediverse instances are running the “Lemmy” software and that’s why they look and feel very similar. Where they differ comes down to the people running a particular instance, since they will have different rules for what you can do. You can find that information in the sidebar.Now all of the Fediverse platforms use a common and agreed upon language to talk to each other. Because Lemmy, Piefed, and Mbin software all use this language and follow a similar format, you can easily share content between all of them. That is what the second guide page talks about. They all have communities, posts, and comments, and work in a similar way.
Usually people make one account on a forum/threaded instance (Lemmy, Piefed, Mbin), and one account on a microblogging instance (Mastodon). This is because the format of microblogging (ex. Twitter) is pretty different from that of forums (ex. Reddit), although it is technically possible to cross post in between them.