"International Edition" generally means printed significantly more cheaply, and not intended for sale within "rich countries"; generally countries where they can realistically push the expensive version. International Editions often say on them "Not for sale in the US" or some such, depending on the publisher; they sell in poorer countries at a lower price.

The quality is often, in my experience, significantly lower; the paper is thinner, the ink cheaper, sometimes the alignment of the printing is a little off. Colour plates are missing or decoloured, hardbacks become softbacks, and so on. But, the words are the same, and sometimes the International Edition is actually pretty reasonable quality. I've got some that are clearly pretty shoddy, and some that you wouldn't actually know were Internationals. I suspect that sometimes publishers don't reprint it cheaply; they just stamp some of them "International Edition, not for sale in countries <x y z>" on it and ship them abroad to sell, much as some semiconductor manufacturers' cheaper chips actually come off the same line as the expensive ones, and then get tweaked (or even just labelled down). A sale is a sale.