What is federation?
Federation is a form of decentralization. Instead of a single central service that all people use, there are multiple services, that any number of people can use.
|Grade of centralization||Examples|
|Centralized||Twitter, Facebook, Instagram|
|Federated||Email, XMPP, phone networks, physical mail|
|Distributed||BitTorrent, IPFS, Scuttlebutt|
A federation linked website can operate alone. Just like a traditional website, people sign up on it, post messages, upload pictures and talk to each other. Unlike a traditional website, however these websites can interoperate, letting their users communicate with each other; just like you can send an email from your Gmail account to someone from Outlook, Fastmail, Protonmail, or any other email provider, as long as you know their email address, you can mention or message anyone on any website using their address.
What is ActivityPub?
Societal uses a standardized, open protocol to implement federation. It is called ActivityPub. Any software that likewise implements federation via ActivityPub can seamlessly communicate with Societal.
The fediverse (“federated universe”) is the name for all websites that can communicate with each other over ActivityPub and the World Wide Web.
The fediverse does not have its own brand, so you might more often hear “follow me on Societal” than “follow me on the fediverse”, but technically the latter is more correct.