Dynamic HTML is a term that is often overused. Basically any webpage that you create using notepad or any other text editor is a static HTML page. This means that the content of the page doesn't change unless you edit the page itself.
Dynamic webpages are webpages whose content changes based on a variety of variables.
The webpages may look different for a user using Netscape then it would for a someone using Internet Explorer. It may look and behave differently if you where coming in from on campus or off campus or if you had a certain type of plug-in. Some of the methods include Scripting Languages - JavaScript, VBScript, etc. These are components that allow web developers to create server-side scripted templates that generate dynamic, interactive web server applications. By embedding special programatic codes in standard HTML pages, a user can access data in a database, interact with page objects such as Active-X or Java components, or create other types of dynamic output.