Simple gears are mechanical devices that transmit motion and force between rotating shafts. They consist of toothed wheels that interlock, allowing one gear to turn another. The size and number of teeth on each gear determine the speed and torque of the output. These gears are commonly used in various machines, such as bicycles and clocks, to control movement. When a smaller gear turns a larger gear, it increases torque but decreases speed, while the opposite occurs when a larger gear drives a smaller one. Understanding simple gears is essential in fields like engineering and robotics.