A common manifestation of noise in black and white images takes the form of isolated BLACK pixels, or pixels regions, in a background of WHITE pixels. This kind of noise is normally called "speckle noise".
In grayscale images the noise manifests itself as unevenness in background regions and imparts a bumpy or jagged appearance to otherwise smooth regions of intensity.
Different procedures are used to remove noise from black and white or grayscale images (color images are not supported). In black and white images noise can be removed only from images with a white background. In grayscale images, noise removal also softens (blurs) the image a bit.