What is the meaning of a rationing book World War 2?

America wanted to win World War II, which required shifting distribution of goods from civilians to the military effort. A rationing book allowed a civilian to purchase only so much sugar or gas or butter in a week. You couldn't buy as much as you wanted, only as much as allowed, regardless of how much money you had or how much stuff the store had. Most families could only buy 3-4 gallons of gas a week.