If you are familiar with your physics, garage door springs are helical springs that exert a rotary force or torque. Functionally, their ends are attached to other components that rotate around the center of the spring and it, in turn, pushes them back to their original position. The bending stress that these springs are subjected to allow them to hold an attached mechanism, such as your garage door, in place. Your garage door torsion springs are what keeps these functional and able to remain open and closed. The tension withstood by these limits the strain on the garage door opener and the door itself. If they were to break or snap out of place, your garage door becomes heavier to lift.