The engine is the same as any old lawn mower you have had.
The CVT is what throws folks off.
Maybe this will help some... There is a large spring that holds the rear pulleys closed. That makes the belt ride high on the pulleys, and holds a low gear.
The front pulley has "rollers" inside. They are basically weights. As the rpm goes up those weights force the rear spring/pulley to open, and that raises the gear ratio.
Lighter rollers take more rpm to open the pulleys, and heavier rollers open it w/ less rpm.