Edit: I appreciate everyone who took their time to comment and provide explanation. All the comments were really helpful and informative. Thanks.
Fediverse is like the United Nations and instances are the countires. Countries with good relations communicate (federate) with each other but the ones that don’t respect our values we might cut communications with (defederate). These defederated countries still continue to exist and there are people within those country that talk with eachother aswell as other countries they do get along with but they’re essentially secluded from the rest of the world. However despite the defederation they still are in principle compatible with the rest of the world so we can open back the communication again if we so decide.
Other social media platforms like Instagram and Twitter are like the animal population; they too communicate within themselves but we don’t have a common language and thus will always remain incompatible and can’t ever federate with them and they (Twitter and Instagram) can’t with each other either.
Federation is when instances exchange information. For example, you posted to lemmy.ml, while using lemmy.world, and I’m seeing this post and replying to you from lemmy.max-p.me. That’s federation in action, in this case with 3 instances involved. It runs on my server entirely in my control, I’m the admin of it. It’s completely independent from lemmy.ml and lemmy.world but they all talk to eachother.
An instance is one website running lemmy. Lemmy.ml and lemmy.world are two examples. There’s hundreds of them, all operating independently and sharing information.
Defederation is essentially when federation is cut off from a given server, think banning an entire instance essentially.
The fediverse is the name of this whole system: it’s federation and universe smushed together, fediverse.
Cross-platform instances would be instances that can talk to multiple platforms. For example, Kbin lets you browse Lemmy threads and Mastodon microblogs from the same place. Mastodon users can somewhat see Lemmy posts. I’ve never seen it referred to as cross-platform though.
But why are there so many instances and from what I have seen they are mostly similar to each other in terms of features and such? Like why would one use lemmy.ml over lemmy.world or vice versa when they are federated?
Because instances are hosted by individual hobbyist and not a company that makes profit, the amount of data that an individual instance can store and process is much more limited by their hardware. Spreading the load across numerous hosters allows for a higher capacity of data storage and therefore total lemmy users. Because of this i encourage you to use more niche instances if they suit you.
As for why one would choose a particular instance over another; you’ll find the each lemmy instance typically has its own social ecosystem and political consensus, because of this certain users will gravitate to the one that suits them best. For instance, lemmy.blahaj.zone is very LGBT heavy with an emphasis on the T, lemmy.world is quite liberal, lemmy.ml is typically socialist, hexbear.net is communist, and lemmy.dbzer0.com is pirate. While many of these are federated with eachother you will often notice an emphasis on certain subjects on an instance by instance basis
I wanna add, that these niche hobby servers do have a higher risk of dropping permanently if the owner decides they don’t enjoy it. No a real reason not to use them but good to know regardless.
Rip lemmy.villa-straylight.com my first home
federation is a trust relationship.
In the context of fediverse, is server operators allowing other server operators to read and write between each other.
For example If Nextdoor federated with MySpace, a Nextdoor account could post something and a person on MySpace could see it in their feed.
Federation is one website simultaneously hosting and displaying content from another. Defederation is rejecting or rescinding federation. Not sure about the last.
