Why is there a need for both HTML and HTML5?

Question

Why have two separate entities when they could have one that encompasses aspects of both programs?

Answer 1

It's simple!

Like before going for college we've to go to school for better understanding of basic elements of education, i.e language, maths and science.

Like wise HTML5 is an advanced version of HTML, HTML introduces you to basics of web document structuring and HTML5 takes you further with new added technologies like geolocation, canvas, offline storage etc.