This sprint car is designed so at high speeds the wings create a downward force to keep it on the track. this force is called ground effect. The wings on a sprint car and Indy racecar act like the wings of an airplane. Bernoulli's Principle states that as the speed of a moving fluid increases, the pressure within the fluid decreases.   The fluid can be liquid or gas, in the case of planes and automobiles it will be refered to as gas/air. The plane wings are built so the air moves faster above the wing creating  less pressure and the air moves slower under the wing so the pressure is greater, thus lift is created and the plane is able to take off, stay in the air and land safely.
      The difference between airplanes and racecars is that lift is not the desired effect, so the wing is upsidedown to create the downforce necessary to keep the car stuck to the ground through cornering manuvers.