Okay, apologies for the many unanswered questions that are slipping past, am trying to answer as many as possible.
My timeline has just frozen completely.
Please check sites like https://fedi.tips and https://github.com/joyeusenoelle/GuideToMastodon/, they will answer lots and lots of common questions about Mastodon and the Fediverse!
If you are a techy person who wants to see technical details, you can find the official Mastodon documentation at https://docs.joinmastodon.org
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All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.