4x4 is a term used to describe four-wheel drive vehicles. When written this way, the first value shows the number of wheels on the vehicle and the second indicates the number of those wheels that are powered while driving. This differs from a two-wheel drive, where only two wheels move with the steering wheel.
A 4x4 is a type of off-road car because it can handle most terrains, but not all off-road cars will be 4x4s..
