The contour that forms a fender begins where the front and back doors end and runs forward or backward either to the front and rear bumpers, and ends at either the hood or the lid of the trunk. This is why minor car accidents are called fender benders, because damage to the bumper could also bend the sheet metal of the fender.
Fenders are designed to avoid wind resistance and make the vehicle more aerodynamic, as well as to keep off mud, pebbles, and other road debris from splashing on and scratching the coat of your vehicle. Frequent bumps and accumulated mud and dirt could cause a vehicle's coat to rust and chip off, and you would have to repaint your car every now and then, apart from having to wash it more often than is necessary. To the practical motorist, fenders are thus essential.
Fenders also add sufficient housing for the wheels, especially the bigger ones, because of their openings which are also usually bigger compared to the stock. They come in many different sizes, designs, and colors for many different types of cars. There are truck fenders, pickup fenders, and car fenders, among others, to choose from, depending on the kind of vehicle that you have. Apart from being universal, most fenders are also customizable, so it is not really difficult to find one that fits your vehicle perfectly.