what r Java server pages ?

Java Server Pages (JSP) is a technology that lets you mix regular, static HTML with dynamically-generated HTML. Many Web pages that are built by CGI programs are mostly static, with the dynamic part limited to a few small locations. But most CGI variations, including servlets, make you generate the entire page via your program, even though most of it is always the same. JSP lets you create the two parts separately. A JSP is first parsed into a java source file which is then compiled into a servlet class. This occurs when the page is first requested, so there is a performance hit at that point. But if you design your JSP carefully the performance of the class, once compiled, should be equal to that of a purpose-built servlet. It is possible to view the servlet source code that is generated by the parser, but it's not recommended that you alter it.

Honestly I would not worry about JSPs until you have got a good grounding in the basics of Java. JSPs are simply HTML files with bits of Java plugged in to generate dynamic content. http://en.wikipedia.org/wiki/JavaServer_Pages