Air intake supports a mechanism, which cools down the air going in to your car increasing the power of the engine. Without this, the engine gets hot and can even get vulnerable to explosion. It can also give your car a decent look and the engine a better sound and that is why it comes in various colors and materials.
The general mechanism is to take the air inside into an air intake tube where the air gets cold and pass it from there. The opening where the air intake happens is called intake snorkel. It is where the air was taken inside that can smoothen the air flowing. Hence, the size has to be big enough and with sufficient amount of air that can pass by. The intake snorkel however shouldn't be as very large or excessive as air passing by could lead to inefficiency.
There is a heat guard designed especially in the air intake tube to detach and filter the air from the remains of the engine, which allows the air to get in with a comparatively lower temperature. Various materials are used to make Performance Air intakes like plastic, silicone, fiberglass, carbon fiber and even metal. Carbon fiber that is used for making air intakes which does provide a nice and stylish look, it also adds up to less weight to the car for it being light weight, however carbon fiber being too expensive, in a several cases it just does nothing better than sitting there and looking pretty.
One of the huge problems with air intakes is the water. When it's raining, water could be sucked in just like air and it might cause trouble and leave you with zero horsepower even causing a hydraulic blow. A few precautions measures could be taken to avoid this situation like: (1) to drive less and slowly during rainy and wet days, which doesn't really happen all the time since we are almost in a hurry nowadays; (2) a hydro shield could be installed, which stops the water from entering the air intakes. There is something called Dry charger, which has been accepted by lots of people and it is not that expensive, hence it saves a load of trouble.