 The first, which is the larger one, holds water or soup used to produce steam.The second, the smaller pot, which is designed to be placed on top of the first, has a lid, and perforated floor, so that it holds the couscous in place while allowing the steam to enter and seep through the grains.Once the couscous is steam-cooked, the lower pot may be used to simmer and complete its cooking, in order to serve the prepared dish.