Except for the Mercedes Benz G63 AMG 6x6 and Brabus B63 S, sport utility vehicles have two axles. The easiest way to discern the number of axles on any vehicle is to count the number of tires fully visible and touching the ground from one side of a vehicle.
Vehicles with two axles have four to six tires: two on the front axle and two to four on the back axle. Most passenger vehicles, including SUVs, only have two axles. The G63 and B63 S are sport utility vehicles designed to drive in off-road conditions or areas where roads are unreliable, hence the third axle with six-wheel drive.