Butter is a dairy product made from cream which has been beaten until it forms a semi-solid mass. Depending on the butter, salt or annatto (coloring) may be added. Butter is typically available salted and unsalted. In the US the most common packaging of butter is in a 1 pound box divided up into individually wrapped portions referred to as "sticks". Butter contains about 80% fat.
Many recipes call for softened butter. To do this on the counter it could take a half hour or so. You can soften butter in the microwave by placing on a microwave safe plate, then microwave using the defrost setting for about 15 seconds.