4륜구동, or "four-wheel drive" (4WD), is a vehicle system that powers all four wheels simultaneously. This feature enhances traction and stability, making it ideal for off-road driving and challenging weather conditions. It is commonly found in SUVs, trucks, and off-road vehicles. There are two main types of 4륜구동: full-time and part-time. Full-time 4WD operates all four wheels at all times, while part-time 4WD allows the driver to switch between two-wheel drive and four-wheel drive as needed. This flexibility helps improve fuel efficiency when 4WD is not required.