The idea is that the cart store can have many items; but the landing page on another site has just a link for a product.
Rather than launch the entire store that the user now has to navigate through to the desired product from scratch, the link takes the user to the one specific product that they were at on the first web site. And then just check out.
(There would be many cs-cart widgets on many other web sites, but hopefully the widget would be individual product specific)