What is butter?
Butter is roughly 80% fat, 18% water, and a little milk solid, and that mix is what makes it so useful in baking. Solid and cold, it laminates pastry into flaky layers; soft and creamed with sugar, it traps air for tender cakes; melted, it enriches cookies and quick breads.
A US cup of butter weighs about 227 grams — two standard sticks, or 16 tablespoons. Wrappers are usually marked in tablespoons, which makes butter one of the easier ingredients to measure, but weighing is still the most precise option for laminated doughs.