See here, about a quarter of the way down, under the heading, "So what is a library?"
I haven't quite got them sorted in my head myself, but I think they are really like a collection of shortcuts, to folders.
So if you copied the Libraries you'd just be copying the shortcuts, not the actual data.
However, if, instead of opening your Libraries, you open your Users folder, which contains about a dozen folders, (Documents, Music, Searches, Contacts... etc), and copied that, then you would be copying the data.
As usual, I'm open to correction, so please don't take just my word for it!!!