All vehicles have a purpose. Mostly in the mundane section being a general city car. Easily handling lovely roads that may have a few bumps. While others are made for the road, sticking to the track and embracing the veracity of speed and pure ingenuity.
4X4 vehicles embrace this accurate nature in that are made for the off-road experience.
Generally vehicles have a two-wheel drivetrain (transmission, drive shaft and differential) system. Meaning the rotational power, called torque, is transferred via the drivetrain to two of the four wheels. This power can be transferred to either the rear wheels referred to as rear-wheel drive or the front wheels referred to as front-wheel drive. The two wheels which are powered control the movement of the vehicle, limiting you movement to those two wheels.
Where a four wheel drive is a type of drivetrain system which supplies the power to all four wheels. Increasing in traction and overall ability to move over the terrain. Primarily used in bakkies, trucks and SUVs.
Why have all four wheels powered?
When the drivetrain transfers the torque (rotational power) to the wheels it allows for the wheels to move. The traction (the grip of a tyre on a road) allows the vehicle to move forward or backwards. Essentially transferring engine torque into movement. With a four-wheel drive system you have an increased chance of traction as all four wheels are powered. Instead of being reliant on only two wheels to move across the terrain.
4X4 vehicles generally have two ranges being Hi and Lo. Hi allows all four wheels to get power at a fast speed allowing the vehicle to move faster over dicey terrain. While Lo gives more power to the wheels at a slow speed to get the vehicle over any obstacles you may come across on your path. Overall giving the vehicle the “oomph” it needs.