From Nielson Norman Group: https://www.nngroup.com/articles/layer-cake-pattern-scanning/
Summary: When headings and subheadings visually stand out on the page and are descriptive, users engage in an efficient scanning pattern that allows them to quickly find the information that they need.
People don’t usually read every word on a webpage, in an app, or even in an article or text passage. Instead, they often scan — because their experience with many websites has taught them that scanning can deliver almost the same value (that is, amount of information) with significant less time and effort. (Recall that people are naturally efficient and attempt to put in the least possible work for achieving their goal .)
The way in which the page is organized visually plays a big role in how people scan its content. If the page layout allows users to quickly identify the essential information that is relevant to their needs, users will save a lot of effort and will be able to accomplish their goals fast. But, if, on the other hand, the layout does not emphasize the important information, people may miss it and they may end up leaving the site.
Design Herald 