Butter is a dairy product made by churning fresh or fermented cream or milk. In many parts of the world, butter is an everyday food. Butter is used as a spread, as a condiment and in cooking applications such as baking, sauce making, and frying. Butter consists of butterfat surrounding minuscule droplets consisting mostly of water and milk proteins. The most common form of butter is made from cows' milk, but butter can also be made from the milk of other mammals, including sheep, goats, buffalo, and yaks. Salt, flavorings, or preservatives are sometimes added to butter. Rendering butter produces clarified butter or ghee, which is almost entirely butterfat. A firm solid when refrigerated, butter softens to a spreadable consistency at room temperature and melts to a thin liquid consistency at 32–35°C (90–95°F). The color of butter is generally a pale yellow, but can vary from deep yellow to nearly white. The color of the butter depends on the animal's feed and is sometimes manipulated with food colorings, most commonly annatto or carotene.
Sweet butter is commonly used to describe unsalted butter. In regular recipes, you may use salted butter if you like salt, but in baking many people prefer to use unsalted or sweet butter when they call for it. Salt acts as a preservative, so butter without salt will be more perishable.