There's an official manual for Mastodon at the following link:
It covers a wide range of topics, and is intended for users, admins, developers and contributors.
The developers' section also includes technical details of how Mastodon works.
(You can also get to this manual by clicking on the "Documentation" link in the bottom left corner of the web interface.)
@QuickSticks @feditips that's a #CloudFlare site. I suggest this link instead: https://web.archive.org/web/20210316185239/docs.joinmastodon.org/