Question

What does the noise filter effect do to an image

Answer 1

It helps to blend the selection into the surrounding pixels. Noise filter can create textures as well. 

Answer 2

Step-by-step explanation:

Noise reduction helps clean the image from tiny dots that appears on images captured with low lights and high ISO. The tiny dots look like a TV that has bad signal. The noise reduction filter eliminates these tiny dots by adding more pixels to the image. With it you have the control over luminance and color noise. In other works, it can help you have a better definition and sharpness.