What is the difference between 4a 4h and 4l?

4a, 4h, and 4l refer to different drive modes in a 4x4 vehicle. 4a (Automatic) automatically shifts between 2WD and 4WD as needed. 4h (High-range) provides constant 4WD for improved traction on loose surfaces at higher speeds. 4l (Low-range) offers maximum torque and traction for extreme off-road conditions at very low speeds.