Butter, "Butter," is made from milk, fresh milk that has been stirred and some of the water drained off from the thick top layer. Mainly used as a condiment, it is nutritious but high in fat, so don't overdo it.
As early as the 5th century BC, the Mongols in China had developed dairy farming techniques and spread them both at home and abroad. Foreigners call it butter, which is the refined edible oil in the milk that Chinese call cream. The Mongols were the first people in the world to process butter for consumption.
In baking, we generally use butter is unsalted butter, this is because the products containing salt, butter, salt content in the different products is not the same, when baking needs to reduce salt in the formula and bake for most ordinary lovers, is more complex, therefore directly using unsalted butter is ok, and we see recipe on the Internet is also mostly use unsalted butter?formula.