I'm still trying to wrap my head around the whole federation thing. I got my account created on lemmy.ml, but I see that I can set the front page include posts from the whole federation, be it beehaw, etc.
Now I'm confused about actually posting stuff. For example, on the lemmy.ml frontpage sidebar, there's a rule 3, no porn. Is it instance-wide? Or is it just for /c/lemmy community? Can I create my own community with nsfw comment? And if not, can I use a federation to post a nsfw content to an instance that allows nsfw from my account on lemmy.ml?
There's a docs page here: https://join-lemmy.org/docs/en/users/01-getting-started.html, but I feel there needs to be more comprehensive and idiot-friendly ELI5 version of federartion and how is it actually impleemented, because its such a huge paradigm shift which most of people are not used to.
EDIT:
Also, can I create communities cross-instance for example?
You can only create a community on your own instance. But you could be a moderator of a community on a different one.
And anyone can make an instance for anything, even porn. There aren't any Fediverse wide rules. However, other instances can block you if they wish. They probably wouldn't have any reason to unless that instance's users were being a nuisance outside their own instance.