JSP (Java Server Pages) is a technology that uses scripting elements, comments, and directives to embed Java code in HTML pages to create dynamic web content. The main scripting elements in JSP are scriptlets that contain Java code in <% %> tags, expressions that output dynamic content in <%= %> tags, and declarations in <%! %> tags. Directives like page, include, and tag are used to control page attributes and imports with <%@ %> tags. Actions are used to encapsulate reusable code in custom tags.