The Fediverse is a giant decentralized or "federated" network of social media services owned and moderated by the people, consisting of mostly Free Software.
Unlike centralized social media platforms, the Fediverse is not and cannot be owned by one person or company and therefor cannot be influenced by the rich and powerful.
There are services for microblogging, blogging, photoblogging, videohosting and much more and they are all interconnected or federated.
So you only need one account to follow users on any of the platforms.
How does the Fediverse work?
What does "Fediverse" even mean?
And what does "federated" mean?
Why use the Fediverse instead of some other social media platform?