1. Social media owned by companies, by their nature, undergo enshittification. It may not be now, but it will happen sometime in the future.
2. If we make social media that is owned and controlled by the people, we can avoid enshittification
3. The Fediverse is an attempt to create social media owned by the people.

All the analogies about email and whatnot, or the comments trying to explain how federation works, they're missing a big part of the question. They're not technically wrong, but those answers are exactly what put me off the Fediverse initially. And I suspect those answer will put off other people, too. And it should be relatively clear why, if you think about it from newbies' perspectives: the question that newbies are asking is what the Fediverse is. Trying to answer how the Fediverse works is avoiding the question entirely. You can't explain the "how" to someone if they don't even know what it is. It's like explaining how to design a software to a caveman, without explaining what a software is.