Black-and-white on Fotopedia

Black-and-white as a description is also something of a misnomer, for in addition to black and white, most of these media included varying shades of gray. Further, many prints, especially those produced earlier in the development of photography, were in sepia (mainly to provide archival stability), which gave a richer, more subtle shading than reproductions in plain black-and-white, although less so than color.

TEXT FROM WIKIPEDIA, cba SOME RIGHTS RESERVED.

Grayscale

In photography and computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information. Images of this sort, also known as black-and-white, are composed exclusively of shades of gray, varying from black at the weakest intensity to white at the strongest.

Grayscale images are distinct from one-bit bi-tonal black-and-white images, which in the context of computer imaging are images with only the two colors, black, and white (also called bilevel or binary images). Grayscale images have many shades of gray in between. Grayscale images are also called monochromatic, denoting the presence of only one (mono) color (chrome).

Grayscale images are often the result of measuring the intensity of light at each pixel in a single band of the electromagnetic spectrum (e.g. infrared, visible light, ultraviolet, etc.), and in such cases they are monochromatic proper when only a given frequency is captured. But also they can be synthesized from a full color image; see the section about converting to grayscale.