Heading tags are used to display your titles and headings in the correct rank and format – much like a book will have a large title for the book name then smaller titles for each chapter and even smaller titles for subsections within a chapter. The main heading tag is heading 1 and is used as shown:
<h1>This Is The Main Heading</h1>
This Is The Main Heading
Correct usage is extremely important as search engines will look at the content of your headings when they index your site. It’s important they know what the main heading is and how the subheadings and sections of your page flow. This will allow them to show most suitable excerpts from your site to searchers and deliver the correct visitors to your page.