HTML provides not only plain paragraph tags, but six separate header tags to indicate headings of various sizes and thicknesses. Enumerated as heading 1 through heading 6, heading 1 has the largest and thickest text while heading 6 is the smallest and thinnest, down to the paragraph level. This topic details proper usage of these tags.
<h1>...</h1><h2>...</h2><h3>...</h3><h4>...</h4><h5>...</h5><h6>...</h6>An h1–h6 element must have both a start tag and an end tag.1
h1–h6 elements are block level elements by default (CSS style: display: block).2
h1–h6 elements should not be confused with the section element
Heading tags (h1–h6) are not related to the head tag.
Permitted Content: phrasing content
The different CSS-styles for headings differ usually in font-size and margin. The following CSS-settings for h1–h6 elements can serve as an orientation (characterized as 'informative' by the W3C)
Search engine spiders (the code that adds a page to a search engine) automatically pays more attention to higher importance (h1 has most, h2 has less, h3 has even less, ...) headings to discern what a page is about.