To understand the benefits of a "federated" network, you have to understand multiple layers of definitions.
Then you have to understand the main impact of federation: that there are multiple, interoperable providers that you get to choose from, and if you aren't happy with the options, you are free to start your own.
And *now* we get to the part that's important for society: federated systems are resistant to censorship and abuse of power, because there is no single organization to take down, and if users aren't happy with *any* available options, they can create a new one with minimal effort and consequences.
"User-run," I think, gets straight to the last point: Mastodon is better for society because its users control it.
Federation is what gives Mastodon users control over the platform, but I think of that as an implementation detail, not the main point.
@flyingpimonster I like it. Maybe even "the people's social democratic network".
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.