To the question of what is torque; If you remember from physics class, force is an input that changes the motion of an object over time. Torque, for example, a simple linear force can push (or pull) the mass
Measuring the torque of rotating shafts is important for designing, commissioning and troubleshooting any machine. Knowing the actual torque of a shaft, propeller or other rotating part is the only way to know that it meets specifications.