The difference between salted and unsalted butter is simple: about 80 miligrams of sodium per tablespoon. Salt acts as a preservative and prolongs the shelf life of butter. Most people use salted butter, and we often use it in our recipes, but some cooks prefer unsalted because it allows them to control the amount of salt in a dish and preserves the mellow sweetness of butter. If you want unsalted butter, look for the words "sweet butter" or "unsalted." The term "sweet cream butter" is used for both salted and unsalted butter.