A tandem axle refers to a configuration of two axles placed close together on a vehicle, typically used in trucks, trailers, and some heavy equipment. This design helps distribute the weight of the load more evenly across the axles, improving stability and reducing wear on tires. Tandem axles are commonly found in semi-trucks and utility trailers, allowing them to carry heavier loads compared to single-axle setups. The increased number of wheels also enhances traction and braking performance, making tandem axles a popular choice for transporting goods over long distances.