Comment by bluehatbrit

From my understanding of Mastodon, you register an account with an instance and that's where your account and data are stored. You then get an address which is something like me@instance.tld. Federated instances can then connect together to read and exchange information, but for the most part your data doesn't leave your instance. I imagine the idea behind this is you can choose (or host) where your data sits, but still interact with a large network of individuals. That said, my understanding of Mastodon is limited.