ASP is a Server side application which can be executed only from server such as Internet Information Server (IIS) which can include scripts such as JavaScript, vbscript.. DHTML is a Client side dynamic web application though it uses javascript and vbscript, it can not be executed from server.
ASP is the server side language, while dhtml is the dynamic hyper text markup language , it is scripting language it provide plateform to javascript,css and other scripting languages.