Monochrome vs Black and White vs Grayscale

Monochrome

A monochrome image is an image consisting of a single color against a neutral background. For example, old "green screen" monitors were called monochrome monitors because they used a single color (green or amber) against a neutral background (black). All black and white images are monochrome images, but not all monochrome images are black and white. For example, a monochrome image might consist of black on yellow.

Black and White

A black and white image is a specific type of monochrome image which uses black against a white background.

Grayscale

Graysacle is a method of representing black and white images on a computer. Grayscale images are represented using only 256 shades of gray rather than the full pallet of colors.

RGB (Mode)