@aral the words you are looking for to describe specific decentralized architectures are:
- peer-to-peer
- federated <--- this is ActivityPub
the difference between a federated and p2p network is the relation that users have to peers. federated systems *are* p2p in a sense, but the "peers" in the network are also intended to serve clients.
a true p2p system like #ssb or #ipfs has a ~1:1 mapping between clients and users. all clients have the same capabilities.