There are two main types of filters in your Audi: engine air filters and cabin air filters. Essentially, both do exactly as their names suggest; they filter out contaminants.
Cabin air filters catch dirt and debris, as well as some allergens, in the air that travels through your heating, ventilation and air-conditioning systems. Essentially, it makes your ride fresher and more pleasant. When you use an Audi Genuine filter, you'll get a cabin air filter that's almost fleece-like for superb performance.
The engine air filter keeps dust and dirt (amongst other particles) from getting into your vehicle's engine. Over time, the engine air filter will grow dirty, and it will begin to lose its effectiveness. When you use Audi Genuine Air Filter elements, you'll get a filter that's made from a paperlike woven fabric; it's moisture resistant, and it has a pleated design to increase filter surface area. The filter paper is embedded in a flexible, heat-resistant compound like the factory original.