The term "undercarriage" refers to the lower part of a vehicle, particularly in heavy machinery like bulldozers and excavators. It includes components such as the tracks or wheels, suspension system, and frame that support the vehicle's weight and allow for movement over various terrains. In aircraft, the undercarriage is known as the landing gear, which consists of wheels or skids that support the plane during takeoff, landing, and taxiing. Proper maintenance of the undercarriage is essential for safety and performance, as it directly affects the vehicle's stability and mobility.