The Fediverse ("Federated Universe") is a decentralized alternative to popular services like Twitter, Instagram, etc.
It uses the ActivityPub protocol, a W3C-standard.
Since Elon Musk has taken over Twitter, Mastodon and the Fediverse have seen a big surge in popularity.
I've compiled a few resources about the Fediverse and Mostodon, both in English and German:
- Fediverse - so geht gutes Social Media
- Kurz und Mündig: Fediverse: free PDF in German
- ActivityPub: Das Fediverse braucht ein einheitliches Protokoll
- Fedi.tips: unofficial guide to Mastodon
- The many branches of the Fediverse
- 10 quick Mastodon tips
- ActivityPub erklärt
- ActivityPub W3C