Let's take an example.
---------------------------------------------------------------------------------------------------
<html> <!--called root tag-->
<head> <!--contains meta information of page-->
<title><!--contains title of page-->
html css
</title
</head>
<body style="background-color:honeydew;">
<!--body tag with style and value-->
<h2 style="color:blueviolet;"> page in html</h2>
<!--applying style with property and value-->
<h1>this is heading</h1>
<!--this is comment of heading-->
</body>
</html>
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note:
on right side of line, we can see written <!--comments-->, it is called comment.
