HyperText Markup Language (HTML) is a simple markup system used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of applications.
Example :
<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
</head>
<body>
<h1>My First Heading</h1>
<p>My first paragraph.</p>
</body>
</html>

The <!DOCTYPE html> declaration defines that this document is an HTML5 document
The <html> element is the root element of an HTML page
The <head> element contains meta information about the HTML page
The <title> element specifies a title for the HTML page (which is shown in the browser’s title bar or in the page’s tab)
The <body> element defines the document’s body, and is a container for all the visible contents, such as headings, paragraphs, images, hyperlinks, tables, lists, etc.
The <h1> element defines a large heading
The <p> element defines a paragraph