You thought you got a beautiful landscape image, but even with such a beautiful subject, the blue of the sky or the green of the grass faded. Has this ever happened to you? It's caused by reflection.
The PL (Polarized Light) filter suppresses reflections and depicts natural subject colors. The PL filter emphasizes the hues of the sky and the contrast of the greenery and curbs reflections from water and glass surfaces, so you get crisp, transparent photos.