4x4 and AWD (All-Wheel Drive) are both popular drivetrain options for vehicles, but they function in different ways.

4x4, also known as four-wheel drive, sends power to all four wheels of a vehicle at the same time. This provides increased traction and stability, making it ideal for off-road or rough terrain driving. 4x4 vehicles typically have a transfer case that allows the driver to switch between 2-wheel drive and 4-wheel drive depending on the driving conditions.

AWD, on the other hand, sends power to all four wheels of a vehicle at all times. This provides improved traction and stability compared to 2-wheel drive, but it is not as capable as 4x4 for off-road or rough terrain driving. AWD systems are typically more complex and can include differentials, clutches, and other components to distribute power to each wheel.

When it comes to fuel efficiency, 4x4 vehicles tend to be less efficient than AWD or 2-wheel drive vehicles because all four wheels are receiving power at the same time. This means that more fuel is needed to power the vehicle.

In summary, if you're looking for a vehicle that can handle rough terrain and off-road driving, a 4x4 is the better option. If you're looking for a vehicle that can handle slippery or wet road conditions, an AWD is a good option. Ultimately, the choice between a 4x4 and AWD will depend on your driving needs and preferences.