Spoilers: Car spoilers have more than aesthetic value. The spoiler is an aerodynamic feature, normally on the rear of the vehicle, that changes the direction of airflow in order to reduce lift and aerodynamic drag.
It gets its name because it "spoils" the normal air flow over the car. Its purpose is to increase the car's grip. Normally what holds the car on the road is its weight, forcing the tyres onto the road surface. Without spoilers, the only way to increase grip is to increase weight, or to change the tyre's compound. However, increasing the weight creates inertia, which has to be overcome when cornering.
The spoiler works like an airplane wing, but upside down. It generates 'down force' on the body of the car. There is a trade-off, however. Every time a spoiler generates down force it also generates drag, the natural resistance of the air to any motion through it. Drag slows down the car. Designers try to maximise the lift-drag ratio, so that the car has just enough force to get around the corners, but not so much that they are too slow.