To understand the benefits of a "federated" network, you have to understand multiple layers of definitions.
First, you have to know what "federated" means in the context of web services. In an age where centralized platforms are the norm, most people have no concept of what a not-centralized platform would look like.
The closest well-known analogy is email, but even that is a bit of a complicated jump, going from direct messaging to social media.
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.
Federation is what gives Mastodon users control over the platform, but I think of that as an implementation detail, not the main point.
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.