Dithering

The basic is, that it is a form of rasterized noise to blend between two values.

It is used in 2D graphics (like pixelart) to fake a gradient or color depth.



In 3D graphics it is used like this sometimes, but mostly to blend between objects. For example: to mask a hard seam between rock and ground.



Or it is also used for masking. Making objects semi-transparent, if the camera is near it, so the object doesn't block the view.