From here
“Spoilers” are called such because their function is to “spoil” the airfoil effect created by the shape of a car moving at high speeds. The rear end of many cars tend to lift slightly at high speed, which can cause instability and even poor handling.
Spoilers should not be confused with wings, which, while often referred to interchangeably with spoilers, serve a different function and often look very different. While spoilers help reduce the lift caused by the airfoil effect, wings create downforce at high speeds. That is, if functional, they actually push down on the car at high speed, to help improve grip and handling. Such aerodynamics are extremely common in competitive motorsports and sports cars. Some car makers (such as Gumpert, referring to their Apollo) go so far to say that their aerodynamics create so much downforce that the car could theoretically drive upside-down in a tunnel.”