HTML is a markup language used to design webpages through tags that describe webpage structure and elements like text boxes and forms. It is interpreted by browsers but does not support data types or programming logic. DHTML allows dynamic and interactive webpages through a combination of HTML, CSS, JavaScript and other technologies. This allows webpages to be animated and content updated without reloading. The key difference is that HTML creates static webpages while DHTML uses additional technologies to make webpages dynamic.