Mashed potatoes are made by placing boiled potatoes through a ricer or mashing with a handheld masher to a point where there aren’t any clumps and then butter or oil and some dairy are added for flavor and creaminess. Smashed potatoes have two different forms.  The first is a more rustic form of mashed potatoes where there are chunks of potatoes and maybe even skin in the potatoes.  Like mashed potatoes they are often flavored with butter and milk.  The second form of smashed potatoes is made by boiling potatoes and then flattening them slightly.  A bit of fat is added such as the chimichurri sauce in this recipe and then they are cooked in the oven to crisp up the edges.