Headings are used to specify the headings of sections or sub-section in a document depending on the desired size of the text,any of six available levels <h1> to <h6> of heading can be used.<h1> defines the largest heading while <h6> defines the smallest.HTML automatically adds an extra blank line before and after a heading tags are paired tag so that it is necessary to and these tags with forward slash / sign.
<h1>This is a Heading</h1>
<h2>This is a Heading</h2>
<h3>This is a Heading</h3>
<h4>This is a Heading</h4>
<h5>This is a Heading</h5>
<h6>This is a Heading</h6>