If the descentralization of social networks continue, we will have to prepare for the eventual rise of the instances wars, where people will start to fight about which instance is better and which one is weird to be in and so on, but that's for the future of us all.
Not quite. Lemmy.world is the instance. I'm from the instance lemmy.sdf.org and I also hang out on feddit.uk . The instance names are just URLs (.world, .uk, and org are all like .com).
Handwavy explanation because I'm fuzzy on details: Federation is the magical interconnection between instance lemmy.sdf.org and instance lemmy.world that allows me to see posts/threads/users on the lemmy.world instance .