Any HTML document starts with a heading. You can use the different type of sizes for your headings. HTML has six levels of headings, which use the elements <h1>, <h2>, <h3>, <h4>, <h5>, and <h6>. While displaying any heading, browser adds one line before and one line after that heading because all heading tags are block level elements.
Example :
<!DOCTYPE html>
<html>
<head>
<title>All Heading Example in HTML</title>
</head>
<body>
<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>
</body>
</html>