A circular polarizer is a type of optical filter that allows light waves of a specific polarization to pass through while blocking others. It consists of two layers: a linear polarizer and a quarter-wave plate. This combination helps reduce glare and reflections, making it useful in photography and other visual applications. Circular polarizers are commonly used in conjunction with cameras to enhance colors and contrast in images. They can also improve visibility in water or glass surfaces by minimizing reflections. Overall, they are valuable tools for photographers and videographers seeking to capture clearer and more vibrant images.