Google likes to categorise websites, pages, elements on a page – well everything really. H1 tags or headings tell Google what the page is about.
Getting this right helps Google to understand where to rank your website pages. You should have one H1 tag per page and two or three H2 tags which indicate key sections of your page. In fact headings go all the way to H6 but the best rule of thumb to remember is the lower the number the more important the information is on the page to Google in terms of ranking the page for relevance. This is why we check you have all your headings in order to optimise your chances of increasing your ranking.