So there is defining locally, normally, and globally (at least I think that's what it's called).
For locally you put local
in front of whatever you are defining. For normal you put nothing. But I can't remember what you do to define something globally (so it can be accessed by any script across the game)
Super easy question because I am forgetful.
You use _G. It's not only for variables either, it can be used for many things. For example:
_G["Print"] = function(printThis) print(printThis) end