About the Fediverse
The Fediverse is a decentralized social media network. Instead of having one single corporation or admin that controls all users across the entire platform, there are thousands of unique "servers" (also called "instances" on the Fediverse) that are all networked together. Each instance sets it's own rules, moderates it's own content, and decides which other servers to talk to or block.
The Fediverse provides a robust solution to online censorship. If you, a user, are banned from one server—simple go join another (or, create your own!). If a specific server is deplatformed by their hosting provider, for example, the rest of the network remains unaffected.
Some servers on the Fediverse have very strict moderation guidelines to promote a "safe space," others take a "free speech" approach, and many are somewhere in the middle. This format allows users to choose what sort of space and community they want to be a part of without necessarily cutting them off from everyone else or forcing extreme groups into isolation and echo-chambers. You can browse the whole network of Fediverse servers to join at: fediverse.party.
Anyone can start their own Fediverse server, although it currently requires some technical knowledge. If you want to start your own server, there are many different options for software to choose from, all which are compatible (for the most part). Mastodon and Pleroma are the most common options.