Refers to anything that actively changes or evolves. For example, a dynamic web page is constantly changing and being updated from multiple sources of input, such as user comments or page elements that are randomly generated. In comparison, static web pages only update when the webmaster manually makes changes to the site.
An example of a dynamic web document is the Computer Hope homepage, which uses a Perl script to pull information from multiple sources. The page is generated dynamically before being shown to the visitor.