Planet gear is a type of gear used in mechanical systems, particularly in gearboxes and differentials. It consists of a central gear, known as the sun gear, surrounded by multiple smaller gears called planet gears. These planet gears rotate around the sun gear while also spinning on their own axes, allowing for efficient power transmission and torque multiplication. This design is commonly found in various applications, including automobiles, wind turbines, and robotics. The arrangement of planet gears helps distribute load evenly, reducing wear and tear, and improving the overall efficiency of the system.