The Fediverse consist of many separate servers, running different software. But they all communicate, they’re a federation of different social networks. This way people on a Mastodon instance can comment on threads on a Lemmy instance, etc.
But similar to banning offending users from communities, there are protections built into the federation. If, for whatever reason, an admin of instance A decides that a specific instance B should not be part of their Fediverse, they can defederate it. Meaning their instance A will no longer pull data (communities, posts, comments) from that instance B. They’re effectively muting the offending instance B from their side.
Users from that instance B can still post/comment on instance A, but users of instance A will never know, as instance A never requests that data. Users on other instances, federated with both instances, will still see it and can decide for themselves of they want to keep it that way.

So if you insist on being a twat on the internet people may stop listening.