Polarizer
The polarizer is one of the most commonly used filters in photography. This filter reduces reflections on glass and water surfaces or paints. At the same time, it increases color saturation and enhances contrast. Objects behind glass (such as shop windows or car windows) become visible again. The polarizer is the only filter whose effect cannot be achieved later through image editing software. Reflections must be eliminated at the time of capture; it is not possible to do so afterward. The CPL filters reflections, increases color saturation, and enhances contrast.

Neutral Density (ND) Filter
Neutral density filters, also known as ND filters, reduce the entire visible light spectrum evenly across the entire filter. Colors and contrasts are not affected.
Filter factor 4 extends the exposure time/aperture increase by 2 stops.
Filter factor 8 extends the exposure time/aperture increase by 3 stops.
Filter factor 16 extends the exposure time/aperture increase by 4 stops.

Filter | In what situation
CPL | In situations where.