Gear shifting is the process of changing gears in a vehicle to adjust its speed and power. In manual transmission vehicles, the driver uses a clutch pedal and gear stick to select the appropriate gear. This allows the engine to operate efficiently at different speeds, providing better control and performance. In automatic transmission vehicles, gear shifting occurs automatically based on the vehicle's speed and engine load. Sensors detect when to change gears, allowing for a smoother driving experience without the need for manual input. Both systems aim to optimize fuel efficiency and enhance driving comfort.