Hi Wayne, did you touch on this later? I don't remember seeing it.
In the mean time, if you want to familiarize more with those concepts, JL goes into it for a couple of lessons here:
HI Rick,
Space can be confusing. That is covered in the Fundamentals of Rigging but Transform Space are the raw input values of the channel boxes.
ie - the exact transforms the user uses.
This is only available in drivers as far as I am aware.
Local Space (bones) are relative to their own rest position, include constraint transformations but exclude any parent transforms.
World Space includes everything. WYSIWYG
In that lesson, we need transform space so the armature constraint doesn't influence the result.
I hope that makes sense.
BTW - it totally normal for it not to make sense for like a long time. You can think of this like a movie and you don't know who the bad guy is. All you need to know is that here is a bad guy, and you will find out who later on.