A garage door torsion spring is a type of spring that is used in modern garage doors to assist in the opening and closing process. It is typically placed above the garage door and is made of large gauge steel wire. The torsion spring works by using torque or rotating force to counterbalance the weight of the garage door, making it easier to lift and lower. This spring tightens when the door is closed and unwinds when the door is opened, storing and releasing mechanical energy in the process. It is an essential component for smooth and efficient garage door operation.