It seems like its just for.memes in general with no specific ...rules but at times it also seems to revolve around LGBQT+ content, also what is with the constant mention of 'rule'?
I've even posted to it before with no dire consequences but I really had no idea what I was doing, thanks!
They are locations that you automatically block once you set up your Lemmy account. They are subs used to test that your Lemmy feed, and blocking mechanism, is working in your client.