Let me try
Bluesky is a more direct successor to Twitter. It's a social media microblog platform (like Twitter and Mastodon) started by some of the same people but with a different focus. It was invite only until last year and operates on an open but different protocol than Mastodon's ActivityPub.
It draws a much different crowd than here, with less focus on FOSS or SW/Dev/Privacy/IT topics
Someone developed a "bridge" between the two platforms for interconnectivity