Creaming butter and sugar is a basic yet critical technique used primarily in baking. Essentially, thoroughly combing the two will incorporate air in the mixture, with the help of leavening agents like baking powder, and will make your breads, cakes, cookies (you name it!) rise
Tip: the end result of your creaming should be a light and fluffy pale yellow mixture.
Photo Credit Rex Roof. CC BY-SA 2.0