The term describes a vehicle drivetrain configuration where the engine’s power is delivered to all four wheels. This system contrasts with two-wheel drive vehicles, which only send power to either the front two or rear two wheels. A typical example is a pickup equipped with this system, allowing it to traverse challenging terrain more effectively.
The significance of this drivetrain lies in its enhanced traction and control, particularly advantageous in off-road conditions, snow, mud, or other slippery surfaces. Historically, this capability has been vital for various applications, including military operations, construction, and resource exploration. Its adoption has significantly improved vehicle performance in demanding environments.