A tandem-axle refers to a configuration of two axles that are positioned close together on a vehicle, typically used in trucks and trailers. This design helps distribute the weight of the load more evenly, improving stability and reducing wear on tires. It is commonly found in heavy-duty vehicles that need to carry substantial loads. Tandem-axles are beneficial for enhancing traction and control, especially when driving on uneven or slippery surfaces. They are often used in commercial trucks, trailers, and heavy equipment to ensure better performance and safety while transporting goods.