What is a stockpile?
A stockpile is all your extra groceries that you got Dirt Cheap. If you buy a couple of extra items at that Dirt Cheap price, when you run out of the one in the kitchen you can go to your stockpile and pull one out that you had gotten at the Dirt Cheap price and you won`t be at the mercy of the store at the full price. That right there saved you money.