All milk has some fat in it. Butter is made from this fat. Butter as we buy it is mostly fat. But some water from the milk is still left in it, and usually a little salt has been added as seasoning. More important, butter has in it some of the vitamins we need to keep us well.
Butter is made by churning milk or cream. Cream is the part of the milk that is richest in butterfat. In a churn the milk or cream is shaken about. During the shaking the tiny particles of fat in the milk come together and form lumps. These lumps are then worked into butter.
The butter used in the United States is made from cow's milk. But butter can be made from the milk of other animals. In Tibet, for example, it is made from the milk of the yak. In many countries it comes from the milk of goats or sheep.
People have known how to make butter for thousands of years. They may have found out how by accident. The first churning was probably done by shaking milk in a bag of skin.
