Header tags define the structure of your site as far as heading go. What is a heading? Headings are basically headlines for your content.
Its very Important for your site because search engines check every pages header tags.They are grouped within <h> tags and go from H1 – H6. They are located in the <body> of your page.
<h1> Header Tag Importance <h1>
Next
<h2>Header Tag h2 <h2>
Next
<h3>Header Tag h 3<h3>