British and North American butters are churned from fresh Butterfat Cream (the cream in which the butterfat in the milk has been extracted from the rest of the milk.)
The Butterfat cream is pumped into churns, which churn out Sweet Cream Butter and its by-product, high-fat Buttermilk. The high-fat Buttermilk is whizzed again to get any more Butterfat out of it that can be obtained, then the remaining milk is dried for commercial use in items such as cake and pancake mixes, etc.
Sweet Cream Butter is usually salted after it has been made, but is also sold unsalted. Whether salted or unsalted, it is still termed “Sweet Cream Butter.”
The butter is called “sweet” because the cream used was “fresh” or “sweet”, meaning as opposed to “sour.” Cream for cultured butter is soured first before the butter is made.