1-bit
1-bit is the most extreme form of monochrome display, using only two colors: an "off" color and an "on" color, usually (but not always) black and white. No intermediate shades are possible, so visual tricks such as dithering and crosshatching are frequently used to create the illusion of shading.
A telltale sign that something is 1-bit rather than merely black and white is if there are jagged pixels, as there is no anti-aliasing or translucency to smooth out lines.
Primitive or simple digital art platforms, such as the original 1985 version of Microsoft Paint and the image post editor on Miiverse, are only capable of drawing 1-bit graphics.