Butter is a dairy-product, derived from milk. Any mammal can produce the milk, but it usually comes from cows. Butter is used worldwide in several ways, i.e. on bread, as a base for gravy for meat or for baking a fancy cake. The word butter is derived from the Greek word bos, which means cow.
Many people think of margarine as a type of butter, but this is a false assumption. Margarine is not a dairy product, because it is made of fats from plants and/or animals. Milk fat or milk solids are hardly used in the production of margarine.