What is the difference between Html button and input type=button?

Almost same, but button with more rendering abilities.


Buttons created with the BUTTON element function just like buttons created with the INPUT element, but they offer richer rendering possibilities: the BUTTON element may have content. For example, a BUTTON element that contains an image functions like and may resemble an INPUT element whose type is set to “image”, but the BUTTON element type allows content.
The Button Element - W3C

References:
http://stackoverflow.com/questions/469059/button-vs-input-type-button-which-to-use
http://web.archive.org/web/20110721191046/http://particletree.com/features/rediscovering-the-button-element/