Okay, so forgive my ignorance, this is all pretty new for me.
Obviously a lot of us are here as Reddit refugees. People looking for a discussion forum that scratches that itch. Fediverse sounds pretty neat. Only I'm not really sure what to make of these instances. Basically, I need a separate account for each Lemmy instance? So if for some reason .world doesn't have what I'm looking for, I literally need to make a new account on someone else's instance? For example, my login doesn't work on lemmy.ca. Isn't the point that you can comment on anyone's post no matter what because it's all run through Activity Pub? Or do I have to make my own instance to federate other people's instances? Super weird.
Am I missing something here? I just want to have a place where I have 1 login and I can see the entire internet's worth of interesting stuff. Like Reddit.
No, a single account on any instance allows you to see and interact with any content on any instance.
Your account on lemmy.world can comment and create posts on lemmy.ca
On the main page, you can adjust if you want to see local posts (only your instance), all posts from all instances, and your subscriptions (can be from multiple instances)
If you go on lemmy.world's main page, you have a section where you can choose subscribed, local, or all posts. All will show you posts from all Lemmy instances, Local will show you only lemmy.world, and subscribed will show you all the communities you've subscribed to regardless of which instance is hosting them.
From there, you can sort by a few other options, like active, hot, new, etc.
No, you don't need to login on other instances. You can subscribe to the communities on lemmy.ca, and then post and comment on them while still on lemmy.world
Then copy that url and paste it into the search box on lemmy.world. Sometimes you need to paste and search a few times - if lemmy.world doesn't know about a community, it has to connect to that instance and try to discover it which can take a few seconds.
Once the community shows up in the search results on lemmy.world, then simply go to it, and subscribe to it. Now you can interact with that community, by liking, posting, commenting, etc, all from your lemmy.world account.
Think of it like one giant company that has that has many separate buildings but all of them are connected via skybridges. Each building has its own community and culture and the ability to create within that building. If you wanted to take a walk to another building and see what they have going on, you can.
If the instance you chose is lemmy.world, that is where you login. I chose lemmy.world because it seemed to run smoother than lemmy.ml at the time I made my account. Other than that it really doesn't matter what instance you create an account on.
Think of instances like email providers. On the front end, you are logging in to your provider. On the back end, all the providers can talk to each other through a common protocol. They can send and receive emails from any other server.
If you are on lemmy.world, you can view, see, and subscribe to content from any server. You can post and comment on any server, but your name will say @lemmy.world if that's your home instance.
From a user standpoint. Make sure you go to lemmy.world, login, and find your content from there. Either through sorting by all or subscribed, or the communities button at the top looking at "all" not "local". If you are a member of lemmy.world and type lemmy.ml into the address bar of your browser it will ask you to log into lemmy.ml when you get there because you are on their site instead at that point. Kinda like having an outlook account and going to gmail.com. You can send and receive email from a Gmail user, but you can't directly go into their site and login just because outlook shares a protocol with them.