Think of a Polarizer filter as Sunglasses for your camera.
What does a Circular Polarizing filter do? What's the difference between a circular and linear polarizer? Along with UV and ND filters, Polarizer filters are among the essential Digital SLR camera filters every photographer should have this filter guide will explain it all. Polarizing filters provide color and contrast enhancement. Reflected light often shows up as whitish glare that washes out color in an image.
A Polarizer filter corrects this problem producing deep, dramatically blue skies. It also removes glare from non-metallic surfaces, such as windows and water. Color saturation in general, especially outdoors, can be improved significantly by using polarizer filters.