Universe Rules OK (I don't think!)

Universes have always been a mystery to me.

Sure, you can't read much TG fiction without coming across Altered Fates or Great Shift, but there are now over thirty different universe categories on the BC fiction submit page, some of which seem pretty specialised such as Aunt Jane, Suitcase or Tuck.

I cannot find comments on the definition of more than a few universes on this forum. Are they defined elsewhere on this site? Surely, it's not a case of making up your own rules as you go along?

Does the very act of creating a universe mean that the author is happy for others to write stories in that universe, without specifically asking their permission?

Can anyone orginate a universe? For example, I have often thought there ought to be a Real World category, in which magic, fantasty or way out science fiction is barred. Can I simply make up some rules and post them - and if so, where do I post?

From a Confused member of the universe (I'm not certain which one!)