Wax is a protective layer applied to the car outer surface to make keep it shiny all the time, prevent oxidation of metallic part with contaminants like salts, oils etc and protect car from UV light. Traditional wax comes in paste form. But these days, wax is available is liquid form and is sprayed over the car surface. Polish is in liquid form and works differently. It removes a thin outer layer of the surface. It also removes minor scratches and dirt. Regular polish is not preferred since it can remove the car paint. Wax after Polish is often preferable. If you have a new car and you are using wax on regular basis, then you need not to polish it for years.