I am currently using Lemmy.zip through the app voyager.
I can also see content from other places like hexbear and fedinsfw.
If I login to lemmy.zip on a desktop I can use my voyager credentials. But I am only able to view lemmy.world and nothing else here.
If I login to fedinsfw on desktop I can seemingly access a multitude of places such as I can on voyager, including lemmy.zip.
I’m sorry if this is such a dumb thing to get confused about. I’ve heard explanation for what all this is, but I’m still just not quite sure I understand.
Instances may have different focuses, e.g. ani.social being focused on anime, hexbear.net on communism, and lemmy.world being generalist.
Instances may also use different software, like mine which uses Mbin, FediNSFW (successor of LemmyNSFW) using PieFed, Mastodon.Social using Mastodon, etc. And each software has a different focus in design and functions.
An instance may also block communications with another, e.g. if a given instance is rampant with bots and scammers, the two involved instances are not aligned ideologically, and so on.
Also on a small tangent, this “defederation”, the process of blocking communications with another instance, is to be expected. Instances won’t always align, and I’d be concerned if they always did. But if you’re ever caught in the cross-fire, it’s easy to mitigate, like with having an alternative account here or there, and/or by using RSS feeds for your followed communities and users as the fediverse is full of those (plus Lemmy and a few others have hardcoded links for searches so you could easily add a redirect script).
I think I’m understanding it a bit better, but in a very broad kind of way.
It can be quite a lot to wrap the head around, yeah.
Imo, it’d be better to stick to using whichever instance you picked, and maybe using another instance, preferably with another software, to see what’s about. Mastodon is what I’d suggest for minimal overlap with Lemmy. Later, you could check something like Mbin, Friendica or PieFed for a reason you may notice as you rotate between Lemmy and Mastodon.