According to wiseGEEK: A root cellar is a structure which is designed to keep vegetables and some fruits at a stable, cool temperature which will prevent them from rotting or otherwise going bad. Root cellars were once a necessary fixture in any home where people wanted to be able to eat vegetables and fruits during the winter, and they are often present in older homes built through the early 20th century. In addition to being used to store fruit and vegetables, a root cellar can also be a useful place to store dairy products, grains, and a variety of other foodstuffs.
Read the rest of that wiseGEEK information by clicking here.
It seems as though root cellars may be making a comeback.
Here, read this article: THE RETURN OF THE ROOT CELLAR
Perhaps, you might be interested in reading A Root Cellar for Your Homestead as well as Building A Root Cellar. And, one more for you: The Complete Root Cellar Book Building Plans, Uses And 100 Recipes.