The companies and articles on this page are focused on improving the exterior of your car. More downforce, less drag, better looks. Body kits have a massive stigma, most of which stems from the golden 80s and 90s where the looks were outrageous and function was a distant second from how the parts performed.
The fact is if you can reduce the air going under the car you will improve fuel economy by reducing drag and also increase high speed stability. Wings and canards are self explanatory. Wing arche body kit and fender extensions make room for bigger and wider wheels which increase grip. The fact that they improve the looks of a car is an added bonus.