JavaServer PagesTM (JSPTM) technology allows web developers and designers to rapidly develop and easily maintain, information-rich, dynamic web pages that leverage existing business systems. As part of the JavaTM family,
JSP technology enables rapid development of web-based applications that are platform independent. JavaServer Pages technology separates the user interface from content generation enabling designers to change the overall page layout without altering the underlying dynamic content.
this has been taken from:
http://java.sun.com/products/jsp where you can read much more.