@maddyy/born2race: Side skirts basically create downforce and make the car stick to the road at high speeds thereby increasing road grip and overall maneuverability and stability. A formula-one car with proper side skirts can travel upside-down in a tunnel...such is the amount of downforce.
In this case, however, its basically eye-candy and cosmetic appeal. Proper side skirts almost touch the ground to prevent air escaping from the side.