History
HTML was developed by Tim-Berners lee in 1990's. HTML was originally based on SGML(Standard Generalized Markup Language)
Introduction
Html stands for Hypertext Markup language. Without it no website can be built, sites like Google, Facebook, Twitter are built on html. It is the skeleton(frame) of every website you view on the internet.

Difference B/W HyperText and LinearText
LinearText
You could say text written on a book, magazine or news paper is called linear text.
HyperText
The web written text including the hyperlink(link) on it is known as hypertext that's why HTML is a HyperText.
What is HTML5?
HTML5 is a new big version of HTML. It is based on many technologies like Geolocation, Offline Storage, Drag n Drop, Canvas(for animation and drawing directly on a web page), WebGL(3D on website) and much more.
Syntax
<!DOCTYPE html>
<html lang="en">
<head>
<title>Hello World</title>
<meta charset="utf-8" />
</head>
<body>
<h1>Hello World</h1>
<p>My first webpage.</p>
</body>
</html>
This is the basic syntax of html.