Gears are toothed mechanical transmission elements that are used to convey motion and power between machine components. Gears mesh their teeth with the teeth of another corresponding gear or toothed component when they operate in matched pairs, preventing slippage during the transmission process.

Since each gear or toothed component is attached to a machine shaft or base component, when the driving gear (i.e., the gear that provides the initial rotational input) rotates with its shaft component, the driven gear (i.e., the gear or toothed component that is impacted by the driving gear and exhibits the final output) rotates or translates with it.

The transmission of motion between the driving shaft and the driven shaft might result in a change in the direction of rotation or movement, depending on the design and construction of the gear pair. Furthermore, if the gears are not of similar size, the machine or system has a mechanical advantage, allowing for a change in output speed and torque.