As I may have mentioned before, I have an obsession with cars and specifically expensive cars. Growing up, the aesthetic appeal drew my attention, but as I now have my license it is a mixture of the ride as well as the beauty of the car (Yes, I still enjoy driving even in my minivan). Anyway, fast cars usually have an extreme look to them which serves two purposes. First, it makes sure people know you spent a ton of money on the car, but also it functions as a way for the car to generate downforce and therefore go faster. Downforce in the realm of car racing refers to the force the car pushes against the road underneath it, which means that the downforce is the normal force as well. Since the force of friction is the product of the normal force and the coefficient of friction, a higher downforce will create a greater frictional force between the car and the road, which prevents the car from sliding in corners (allowing the driver to take corners faster).  Downforce also helps on straight sections of the racetrack as the greater frictional force allows the tires stay spinning, without slipping or burning out. Basically, downforce gives the car more traction, keeping it tight to the road. 

One simple method of increasing downforce is adding rear wings and spoilers, as the air rushing over the angled spoiler pushes the car down onto the road. Companies such as Lamborghini and Mclaren have adapted to increase the efficiency of their cars by having wings and spoilers that actually come out of the shell of the car at certain high speeds. F1 racing cars can actually provide up to a maxiumum of 5 times their weight in downforce, and most of that work is done by the wings (front and rear) and the diffuser. The diffuser works by going at the back rear of the car and converting the high velocity, low pressure air from underneath the car into low velocity, high pressure air at the rear of the car, creating a vacuum effect due to the Venturi effect. This extremely low pressure underneath the car in comparison to the higher pressure above the car creates even more downforce, making diffusers essential to F! racing and other sportscars. A very basic way to look at it is that fast cars are designed opposite of airplanes: airplanes' wings are designed to create lift and keep the airplane suspended in the air at high speeds, while cars are designed with negative lift (downforce) to keep the car on the road with as much traction as possible. In the video you can see just how fast the F1 cars can go around corners due to this downforce. 

Often, engine specifications and horsepower are seen as the reason for the speed of a car, but in reality a v8 can go faster than a v12 and vice versa because a large factor is balancing the downforce and the drag to maximize speed in corners and straight sections, which is why the design of a car's aerodynamics and small parts such as diffusers are so important.