Spoilers used to be an exotic accessory for cars back in the 70's and 80's. They waned a bit in the 90's and naughties but have an uncanny ability to keep their spot on affectionados list of extras. There are plenty of cars on the road these days that have rear car spoilers, but do they make any difference to the cars road holding? More importantly, do they make the car go faster?
I understand that initially the rear spoiler was attached to race cars in order to improve the aerodynamics and force the rear wheels to the ground in order to increase grip and road holding. However a car that is driving at speeds between 60 and 100 kph I would assume does not really run the risk of lifting off the ground but does it provide the car with more fuel efficiency and driving comfort? The term 'spoiler comes from the word' spoil 'which means that it is trying to spoil or deter obstructive air movement across a body of a car in motion
The spoilers that are at the front of the vehicle are called 'air dams'. These are installed in order to prevent the car from lifting due to too much air going under the front of the car. There are various spoilers that are added to cars for the purpose of styling and have either little aerodynamic benefit or they sometimes even make the aerodynamics worse.
There are many different types of spoilers that are used on both racing and passenger vehicles.
The famous Porsche 911 introduced a large spoiler back in the early 70's, which ended up being termed the 'whale tail'. This was designed to reduce rear lift with such a small, lightweight car. There have been many different alterations to the whale tail over the years by Porsche but it also made the car one of the most recognizable sports cars in history.
The same design of the whale tail then flowed through the development and design of various other vehicles such as the Camaro, the Saab and even flowed into designs of small kids bike, boats and trucks. Even car roof racks have been made with spoiler-like aerodynamics in mind.
The bottom line is that spoilers can make a difference to the handling of a car but I suspect the difference is very marginal at normal city driving speds. But plenty of people like the look, that's for sure, and if it's designed in accord with the overall design of the car then fair enough, they can look pretty good!