Use h1 to h6 elements only for headings. Do not use them just to make text bold or big. Use other tags for that.
<h1>
</h1>
<h2>
</h2>
<h3>
</h3>
<h4>
</h4>
<h5>
</h5>
<h6>
</h6>
<h1>
This is heading 1
</h1>
<h2>
This is heading 2
</h2>
<h3>
This is heading 3
</h3>
<h4>
This is heading 4
</h4>
<h5>
This is heading 5
</h5>
<h6>
This is heading 6
</h6>