The term axle is loosely used to describe the shaft or two half shafts connected to transverse wheels. It can be a load bearing shaft or a shaft that drives the wheels on a .
On a rear wheel drive vehicle, the power to the wheels comes from a propeller shaft which runs under the centre of the vehicle, front to back, from the gearbox to the differential drive which is located centrally between the two rear wheels. The differential is a set of cogs which turns the drive rotation ninety degrees to each back wheel. The Differential, through the clever design and setup of the cogs, allows the rear wheels to rotate at different speeds necessary when the vehicle is turning. The term rear axle can refer to the complete set of two half shafts or half axles and the differential.
On front wheel drive vehicles there are two half shaft/axles connected from a differential usually combined in the gearbox via constant velocity joints which allow the front wheels to rotate for steering the vehicle while under torque from the rotating shaft/axle. These CV joints are usually encased in a rubber sleeve containing lubricant grease. The rear wheels of the front wheel drive vehicle have stub axles which are usually short and part of an independent suspension system on each rear wheel.