JSP stands for Java Server Pages. Basically it's a way to write dynamic web pages that make use of some special tags. These pages and tags are translated at runtime into Java programs (called servlets) that reply to user requests for a specific URL with the dynamically generated HTML specified by the page and the tags that you wrote.
For more information, check out Sun's website for JSP.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.