Image noise is interference in the video signal that shows up as grainy specks. It can be caused by low lighting situations, a nearby power interference, heat, or device algorithms.
DNR is a technique of removing image noise from a video signal by applying a digital comb filter. It makes images clearer and reduces video file size.
A 2D filter reduces the noise that can be found in low light images. This type of filter is sometimes confused by motion, resulting in blur trails.
A 3D filter goes one step farther and effectively reduces the noise in static images and images with movement.