As the fan blades turn, they force air forward, toward the exhaust port (check out How Airplanes Work to find out what causes this). When air particles are driven forward, the density of particles (and therefore the air pressure) increases in front of the fan and decreases behind the fan...
They are autonomous vacuum cleaners that operate as carpet sweepers and vacuum cleaners at the same time. They usually return to their docking station to recharge batteries. Some models can even empty their dust containers into the docking station. Robotic vacuum cleaners are great for home use –...