Headings give you a great chance to use your focus keyword (or its synonyms) prominently, to make it really clear what the page is about. By adding your focus keyphrase to your subheadings, you stress its importance. Moreover, if you’re trying to rank for a keyphrase, you’ll have to write about it. If none of your paragraphs address the main topic, you’ll probably have a hard time ranking.
From Yoast::