It's basically a "lookbook" concept, which is something you flip through for inspiration and to see what the current trends are. If you want a technical parallel, think Dribbble.

Pinterest takes this and adds a mix of dynamic wishlists and storefronts to it - with alerts of price drops, and conceivably price and currency calculation for an international audience down the line.

I generally hate the term, but Pinterest also acts as a more curated lookbook, since you can choose whom you follow to compose your own magazine-like feed.

I don't mean to give the impression that I have any idea about the profitability of Pinterest, because they are hauling a truckload of static content - on Django, to boot.