Polarising filters are useful for eliminating reflections from surfaces such as water or glass and for intensifying the blue of the sky. They will also increase colour saturation, bringing better clarity and contrast.
A circular polariser filter works by limiting or completely eliminating reflections from flat non-metallic substances (it has no effect on reflections from metallic or curved surfaces).
You can control the amount of reflection from the subject by turning the filter’s rotating dial. But the extent to which reflection is eliminated depends on the angle at which light is reflected from the subject as well as the rotation of the filter. To completely eliminate reflection, try to find the camera angle that maximizes the filter’s effect