Your account (and every account) has a home instance. Both you and I have our accounts on lemmy.world.
And every community (aka subreddit) also has a home instance. The home instance for this community happens to be also be lemmy.world, same as our accounts.
But through federation, the posts from each community gets copied from the communities home server onto each subscribed user's home server. So you can subscribe to any community on any server that lemmy.world federates with.

So while it's possible for multiple instances to have an nfl community, it's not necessary since you can sub to the NFL community on another instance and that's totally normal and expected. Think of it as the subreddits name includes its instance name, so [!nfl@lemmy.ml](/c/nfl@lemmy.ml) is just a different subreddit than [!nfl@lemmy.world](/c/nfl@lemmy.world), just like on Reddit you could have competing subs named /r/nfl and /r/nflfootball. And just like reddit, when things start to calm down, I think you will see that in cases where a bunch of dupe subs exist... one or two with active mods start to dominate on user count and those end up being the most interesting. It will be a bit wild west for a while though. Lemmy is a lot smaller than reddit, though, when I find dupes of a topic I care about, my strategy had been to subscribe to them all and I'll cancel the ones that flopped a few months from now when it's clear what is active and what's dead.

[–] Mr_Jabroni@lemmy.world 5 points 1 year ago

Thanks for the link, that clears things up. I'm looking forward for everything settling down a bit, but I will admit the new experience is exciting. I like your idea of just subscribing to interesting stuff and manage it later, I'll start doing that so thanks for the tip as well!

[–] oryx@lemmy.world 4 points 1 year ago (1 children)

So my account's home instance is lemmy.world. Do I need to make a new account to access another instance, or can I use this one across every instance?

[–] baduhai@sopuli.xyz 9 points 1 year ago (1 children)

You can use your account on lemmy.world to access communities in other instances. If you look at my username, you will see that I am replying to you from sopuli.xyz even though this thread is on lemmy.world.

[–] oryx@lemmy.world 2 points 1 year ago

Ah, that makes sense now! I also just learned about sorting All vs Local and commented on a post from another instance. It all just clicked finally!

[–] half_built_pyramids@lemmy.world 1 points 1 year ago (1 children)

How would I see lemmy.ml's main page?

Like I have a local feed here. Is there a way to see another instance's feed?

[–] half_built_pyramids@lemmy.world 1 points 1 year ago

Figured it out mostly. Seems like some instances have a "main" community you can navigate to. Others just have their name, like this instance's lemmy.world's local feed viewed from another instance world be:

https://sh.itjust.works/c/lemmyworld@lemmy.world

Same for looking at lemmy.ml's local feed from our instance:

https://lemmy.world/c/lemmy@lemmy.ml

Or, to use shit again, here's what their main page feed looks like as viewed from our instance:

https://lemmy.world/c/main@sh.itjust.works