Let’s just have a quick look at the jargon, before we continue:
Monochrome: A monochrome image consists of a single color (any colour) of varying intensity against a neutral background. A black and white image is a type of monochrome image, one that uses black and white. All Black and White images are monochrome, but not all monochrome images are black and white.
Tone: When colours are converted to black and white, they become shades of grey, or tones. Light colours become light tones, and dark colours become dark tones.
Tonal contrast: The difference between these shades is called tonal contrast and also is often the difference between a mediocre Black and White image and a great one.
Highlights: These are the lightest tones and this is where the story lies in a Black and White image. Your eye is drawn to the lightest and brightest areas in an image.