The scattered disk was new to me when I researched the Kuiper Belt some while ago, Jilly. I'm not surprised that you aren't clear what it is, because astronomers aren't either! Some put it as an extension to the Kuiper Belt, but others refer to it as a separate region because the objects in it behave differently. If I'm still around when they get enough evidence to decide, I can rewrite the Kuiper Belt
But it's harder to study those outer regions than it is to study galaxies millions/billions of light years away. The galaxies give out radiation and telescopes can detect that. The small, icy bodies that get scarcely any sunlight are very tricky.