Definition - What does Grayscale mean?
Techopedia explains Grayscale
A digital image is composed of groups of three pixels with colors of red, green and blue (RGB), also called channels in digital imaging. Each channel also contains a luminance value to determine how light or dark the color is. To get a grayscale image, the color information from each channel is removed, leaving only the luminance values, and that is why the image becomes a pattern of light and dark areas devoid of color, essentially a black and white image. Most digital imaging software applications, even the most basic ones, are able to convert an image to grayscale. This is also very important when printing, since it only consumes black ink, as opposed to printing in color, which consumes all three print colors (cyan, magenta and yellow) as well as black.