Comment by anotherrandom

Mastodon is a bunch of separate federated Mastodon instances. In order to see content from several you need to connect to each of them (if memory serves, your identity and social graph are not portable between instances due to the limitations of ActivityPub. This is a problem Dorsey's @ Protocol attempts to solve). That does let you see the illusion of centralization though, sort of like email which is also federated