An interesting thing I'm learning as I start exploring the larger #Fediveeerse! is that #instances can each set their own standards for a public face. Some provide a public directory of members, even a public version of their local stream; others give you no information about themselves at all, even how many people belong to it. So some are like closed BBS niche groups and some are giant general interest places like Twitter, but the #ActivityPub #W3C standard lets them all freely communicate.