lemmy & ActivityPub
The ActivityPub protocol is a decentralized social networking protocol based upon the [ActivityStreams] 2.0 data format. It provides a client to server API for creating, updating and deleting content, as well as a federated server to server API for delivering notifications and content.
[Find your old reddit community on the fediverse!](https://sub.rehab/?searchTerm=&visibleServices=lemmy&visibleServices=kbin&visibleServices=misc&visibleServices=matrix&officialOnly=false&newOnly=false) This will show you where your reddit community migrated to: 
Decent article written before Lemmy (when diasopra was the apparent alternative). Still worth reading, especially for those new to the fediverse concept.
Gathering statistics about nodes in the fediverse. https://the-federation.info/info