There are several kinds of springs; however, they all store mechanical energy by deforming elastically. That means, of course, that all springs are manufactured in elastic materials, of which hardened steel is the most common one. Small springs can be manufactured directly from hardened steel wires, but larger springs must be manufactured first and then hardened.
The most common spring is the coil (helical) spring. It is made by winding a wire around a cylinder. This is an example of a type of spring that uses linear forces. Another kind uses rotational force. These are the main categories of springs; however, there are several subcategories depending on the amount of force the spring is supposed to handle, if it is intended compress or extend, if it is supposed to store the energi or absorb it. The spring can also be made in different materials depending on what features it should have or which environment it will be in. Many springs are standard components but some applications require springs built according to certain specifications.