After a clear protection filter, a polarizer is probably the first glass filter which any camera user should purchase. The principal use of the polarizer is to eliminate surface reflections, glare and hot spots from any light source entering the camera. This reflected light often shows up as a whitish glare which reduces the colour in the image. The polarizer is used for colour and contrast enhancement and removes reflections from substances such as water and glass. It can darken a blue sky and increases colour saturation.
When two polarizers are placed together it is possible to achieve near black out, dependent on the angle in which they are aligned. This enables intense effects to be created. One of the polarizers is rotated until the required effect is achieved.
For more information, please view this Polarizers technical data PDF
and this Polarizers PDF
Polarizer glass filters are available in linear and circular varieties: listed below.