the fediverse refers to a "universe" of social networking services that can all communicate with each other over a standard protocol.
sort of like how email is an open protocol and you can sign up with an email provider of your choice (e.g. gmail, protonmail) and send email to anyone else, instead of everyone being stuck within a single provider and unable to communicate with people on a different provider. now for social networking, too! eg, someone on mastodon can see posts from
@threads