Heading semantics (heading-semantic)
Use semantic heading tags like <h1> to <h6> for actual headings.
Paragraph used as heading:
This <p> element is styled to look like a heading but does not use semantic heading markup.
Introduction
This introduction provides detailed information about how to use this ...
The (DOM/programmatic) structure of the above example looks like this:
<p class="heading1">Introduction</p>
<p>This introduction provides detailed information...</p>
<p>This introduction provides detailed information...</p>