why html5 is used instead of html? is it is same?

Answer 1

Html5 is the result of a evolution.
In the first versions the target was to implement and refine the code, in Html5 the main goal is to extend multimedia functionalities without using external plug-ins like flash. Interaction with css and native graphical effects are improved.

Answer 2

HTML 5 is just the most recent version of HTML standards. It does have differences from the previous version of HTML 4, but most of those differences are additions or improvements for cleaner and more dynamic code. However, some HTML elements and attributes are no longer in use and have been replaced by new elements or CSS. If you knew HTML, then learning HTML 5 isn't very difficult.