Re: I'm still playing this game...
A global variable is just one that anything (in the game) can access - it's got global scope in the game. It also stays accessible until it's set to null, so if you use generic names that someone else may use you can run into problems. So if you define a global variable in, say, an actor (e.g. MyActor = self;) then you can call MyActor from any scene or object, etc. until you quit the game (after which you'd have to redefine it).
A global table is just a table that's global - if you get tables, you get global tables
Feel free to pm me if you want some better help, I'll happily try to give it but I don't wanna get too off topic here.