From their documentation: "Radicle adopts a local-first, peer-to-peer (P2P) architecture, which draws inspiration from Secure Scuttlebutt (SSB) and Bitcoin’s Lightning Network.
Nodes on the Radicle network subscribe to repository data they are interested in, and peers announce updates that in turn trigger fetches for the underlying content. Just like SSB and Lightning, updates are gossiped on the network until they reach all interested peers."
Anyways, a good introduction to git-ssb would be this document: https://github.com/hackergrrl/git-ssb-intro