What is the Fediverse?
The Fediverse is a giant Network of Social Media Platforms.
Imagine
Imagine Twitter, Facebook, Instagram & Co were all part of one giant network. That's basically what the Fediverse is, except the parts are less well known, free software & federated replacements to those.
In the Fediverse you can use your "Twitter" account to interact with "Facebook" users, share "Instagram" posts, comment under "Youtube" videos, listen to "Bandcamp" music, follow "Wordpress" blogs, take part in "reddit" discussions and more.
What is "Federation"?
The email allegory
Everybody knows you don't need to be on the same email Provider to communicate via emails. You can send a mail from riseup.net to gmail.com and the other way around. That's about the same way that "federation" in the Fediverse works. Federation just means that different or decentral servers or instances can communicate with each other via a protocol. Just like email uses POP, IMAP or SMTP protocols for federation, the Fediverse uses mostly ActivityPub.
External Links
Fediverse Guides
The Fediverse: the distributed social network
Guide to the Fediverse
DE: Fediverse – So geht gutes Social Media
DE: Das Fediverse