Graduated ND filters, or Neutral Density filters, are photographic tools that reduce light intensity in a specific area of an image. They are typically darker at the top and gradually become clear towards the bottom, allowing photographers to balance exposure between bright skies and darker landscapes. This helps prevent overexposure in the sky while maintaining detail in the foreground. These filters are commonly used in landscape photography, where the difference in brightness between the sky and land can be significant. By using graduated ND filters, photographers can achieve a more balanced and visually appealing image without relying heavily on post-processing techniques.