A box spring is a type of bed foundation designed to support a mattress. It typically consists of a wooden frame covered in fabric, with springs or a solid platform inside. Box springs help absorb shock, provide stability, and can extend the life of a mattress by reducing wear and tear. Box springs are often used with innerspring mattresses, but they can also work with other types, such as memory foam or latex mattresses, depending on the design. They are usually placed on a bed frame and can add height to the bed, making it easier to get in and out of.