For anyone who wants an invitation to join mastodon.online, let me know! Like mastodon.social, it is one of the two official communities run by the Mastodon non-profit. The difference is that mastodon.online is invite-only.
Joining an invite-only server helps keep out spammers who target mastodon.social and lets someone be part of a more exclusive community. This can help someone have a better-quality mastodon experience, overall.
Of course, to keep out scammers, the invitation isn’t open to just anyone who asks, they will have to have a posting history of some sort.
It sounds as though there’s a lot more to these new setups than I had initially thought, this might take a bit of reading just to pin down the basics. Thanks for the detailed response, much appreciated, those links are going to come in handy.