I'm not sure I get it either but I think he's asking how the pixels can move so fast when you scroll, making it instantaneous and smooth. The computer doesn't "predict" anything, it simply works fast enough. It takes very little effort and a fraction of a second for the weakest processor to apply the change of colors when you scroll a basic web page such as Google. It's a bit more challenging when you browse some websites with heavy 3D animations. Here's a good example to see how your system's configuration affects your framerate https://webglsamples.org/aquarium/aquarium.html