What's the basic difference between HTML and html5 ?

Question

does <nav> and <header> etc are used only for organising the page?

Answer 1

There are lots of differences that are given in HTML5. The main difference between HTML and HTML5 is that video and audio are not part of HTML while these both are integral parts of HTML5 specifications.

Answer 2

Vector graphics is also an integral part of HTML5 such as SVG and canvas while vector graphics is possible in HTML with the help of various technologies such as VML, Silverlight, Flash, etc.
In HTML, browser cache can be used as temporary storage. In case of HTML5, application cache, web SQL database, and web storage is used.
HTML doesn’t allows JavaScript to run in web browser, it runs in same thread as browser interface. HTML5 allows JavaScript to run in background that is possible because of JS Web worker API in HTML5.
HTML works smoothly with all old browsers while most of the modern web browsers have started supporting HTML5 specifications. These browsers include: Firefox, Mozilla, Chrome, Opera, Safari, etc.