A 3d shading style created to emulate a "hand-drawn" look on computer-generated images. It is used in games like Genshin impact or Breath of the wild.
A shading style consisting of simple and intentionally non-realistic rendering of light on surfaces with a clear separation of the lit side of a surface from its shaded side, regardless of the intended material depicted, resulting in only two flat color shades. However the final render can (and often does) have added filters, patterns/prints or color gradients native of the object surface itself, or highlights.
It's name is nowadays often used for 2d as well.
For 2d animation, hand-drawn elements are often shaded this way in most anime to make the process less difficult and time-consuming, most notably moving elements in focus like characters and the objects they interact with.
Keep in mind it refers to lighting style when you use this tag.