Cookie jars are utilitarian or decorative ceramic or glass jars often found in American and Canadian kitchens. In the United Kingdom, they are known as biscuit barrels or biscuit jars. If they are cans made out of tinplate, they are called biscuit tins. While used to store actual cookies or biscuits, they are sometimes employed to store other edible items like candy or dog treats, or non-edible items like currency (in the manner of a piggy bank). (source)