Trying to answer the question of "what is Mastodon" more precisely -- is this correct? Mastodon is a) open source software that uses an underlying protocol, ActivityPub, to run servers that allow for federated social communication, and b) an open source client app that talks to these servers and renders information for them from users. In an analogy to email, Mastodon would be both Gmail and a particular software approach for an SMTP server... (contd)
...but just like with email, someone else could write other server or client software and it would still essentially be email. Colloquially when people refer to Mastodon they're often referring to the *network* because these things have usually gone together (social networks live exclusively inside particular software services and apps) but Mastodon is different in this sense -- more like an email app/server or web browser/server. Is this right, Mastodon experts?
ActivityPub is like SMTP and IMAP but for things you usually find in social networks. Mastodon implemented the server-server protocol (~SMTP) to make its Twitter-like instances federate together and with other implementations of AP (YouTube-like PeerTube, Reddit-like Lemmy, Instagram-like PixelFed and so on).
Mastodon introduced its own client-server protocol that makes Mastodon clients basically browsers. Indeed all the logic is on the server and clients are used just to provide a native UI.
Instead AP client-server protocol assumes more logic for the clients and this didn't fit Mastodon clients use case.
To be clear, being a AP network means you can use a Mastodon account to comment a PeerTube video.
Imagine if YouTube channels appeared on Twitter as native Twitter accouts, new videos appear as tweets by those channels and when you comment the tweet it appears as a comment also on YouTube.
This is what happens with Mastodon and PeerTube and to some extent also with other platforms.
