see also human reading
Reading comprehension relies on the twin skills of skimming and scanning, often done together. Depending on what the function of the text is, one skill will be used more than the other. It would be foolish to skim a contract without reading the small print carefully. And if you don’t skim a newspaper article to get the gist of it, scanning for details is meaningless.
Image: A reader highlights text while skim-reading in order to improve retention and to create a hierarchy in a text, applying a style that can be efficiently scanned for at a future time