He is saying Halftones is a part of the light family. The light family in painting is as follows. Source Light Highligt Midtones Reflected light cast shadow Occlusion Shadow shadow Core shadow Subsurface scattering Refracted light and Reflected shadow.

Pff a painter is not going to use the term Halftones to describe midtones. Halftones is a term used in printing and it is a very specific term that describes the pixelitasion of vector images. a fast google will save you the embarrassment next time https://en.wikipedia.org/wiki/Halftone

I know more than just the basics. That is why I am surprised to see someone painting that good and giving lessons to ignore them. It blows my mind. I am here to correct them and not to listen to your bullshit. so if you don't want a down-vote just get lost.