[jake13jake]

the scope of non-prefixed vars:
An NPC's static variables - local to the NPC (can be written x= or this.x=).
Any other vars that are built-in (ex. players, npcs arrays)
A function parameter- local to the function.
Otherwise, it's a global variable that all scripts share.

If you're using a variable temporarily, like send some data into a function and simply returning a value, I'd use a temp.var.