Circular Polarizer: Light rays which are reflected by any surface become polarized and 

polarizer filters are used to select which light rays enter your camera lens. The circular polarizer

filter allows you to remove unwanted reflections from non-metallic surface such as water, glass etc.

It also will enable colors to become more saturated and appear clearer, with better contrast. This effect is

often used to increase the contrast and saturation in blue skies and white clouds.