Impact wrench stores a massive amount of energy to cause a powerful torque that can loosen or tighten nuts. (Available in Corded, Cordless Options & Pneumatic) The regular wrench cannot always loosen or tighten nuts or bolts, especially the ones that are either too loose or too tight to move from their place. This is exactly where the role of this impact wrench comes into play. The energy is stored in the hammer through the repeated rotation, and then that energy is transferred to the shaft on the outside, which is the anvil. This is why this impact wrench is able to generate such strong twisting force.