8 speed multitronic transmission also known as CVT (continuously variable transmission) gearbox allows the wheels to rotate at various speeds, without altering the engine speed. To simplify that, imagine two gears connected by a chain.

The gear connected to the pedals is half the size of the one at the rear wheel. For every full rotation of the pedals, the wheel would rotate half a turn. You would travel slowly, but the pedals would be easy to move.
Swap that around so that the pedal gear is now double the size of the wheel gear. For every full turn of the pedals, the rear wheel would turn twice. It would be really hard to set off, but once moving, you could achieve high speed.

That’s exactly how it works in a car. A conventional manual gearbox will have five or six gear ratios, with the lower set useful for low speed – pulling away from junctions or climbing hills – and the higher ones for cruising on the motorway at low engine rpm.

Normal automatic gearboxes work in largely the same way, except the job of depressing the clutch and swapping the ratios around is taken care of by the car.

A continuously variable transmission (8 speed multitronic) also works automatically to alter the speed of the wheels in relation to the engine, but instead of using a box full of gears, it has a pair of pulleys – which is why it is referred to as a transmission, rather than a gearbox.
One is connected to the engine (the drive pulley) and another to the wheels (the driven pulley) by a special chain, much like the bicycle in our example above.

However, unlike the fixed metal gears of a bike, each pulley of the CVT is able to vary its radius in order to alter gearing, because the pulley is actually a set of cones than can move together or apart.