I have a mastodon.social account from way back (2018) - now I have one here... trying to work out how this works

Mastodon

This Mastodon server is by and for the community of human-computer interaction researchers. On the surface, Mastodon is like Twitter. However, the difference is that it is open-source, decentralized, and federated. This server is sponsored by @Princeton HCI and administered by a growing committee of volunteers.