Header tags (H1, H2, etc.) - definition
Header tags are used by search engines as one of the attributes that help assign rank to a page.
Typically the visual header on the page, and formatted accordingly, the headers and subheads can be tagged <H1>, <H2>, etc., in accordance with their level of importance as a header. Web developers use the tags to tell the search engines the hierarchy of importance.
While most search engines can identify headers by type size and other formatting attributes – it is a good practice to identify the hierarchy in the code.
<h1>This is the headline</h1>
<h2>This is the first subhead</h2>
<p>This is the text that speaks to the subject of the first subhead</p>
<h2>This is the second subhead</h2>
<p>This is the text that speaks to the subject of the second subhead</p>