A spring is a mechanical device that stores energy when it is compressed or stretched. It is typically made of metal and can return to its original shape after the force is removed. Springs are commonly used in various applications, such as in mattresses, automobiles, and toys, to provide cushioning or to absorb shock. There are different types of springs, including compression springs, which are designed to be compressed, and tension springs, which are designed to be stretched. Another type is the torsion spring, which works by twisting. Springs play a crucial role in many everyday objects, making them essential in engineering and design.