Rationing is taking minimal amounts of a supply in order to have it last as long as possible. It's good when supply is scarce. Some items that were rationed include gasoline, bicycles, footwear, silk, nylon, fuel oil, stoves, meat, lard, shortening and oils, cheese, butter, margarine, processed foods, there are many more...
Rationing was important to make sure no one got to much food. And because the supply of food was so little they had to rations. Goods rationed where eggs, milk, bread things like that