JSP technology is used to create dynamic web application same like Servlet technology. It is another web technology given by Sun MicroSystem for the development of dynamic web pages an the client browser. It provides a tag based approach to develop java web components.
JSP have .jsp extension, we can directly access these JSP pages from client system browser window. Because jsp pages are contains outside of the WEB-INF folder.
A JSP page consists of Html tags and JSP tags. The jsp pages are easier to maintain than servlet. It provides some additional features such as Expression Language, Custom Tag etc.
A JSP is called as page but not program because a JSP contains totally tags. Every JSP is internally converted into a Servlet by the server container.
Why JSP ?
The first technology given for the development of web application is CGI. In CGI have some drawback, So Sun MicroSystem develop a new technology is servlet. But working with Servlet Sun MicroSystem identify some problem, Servlet technology need in depth java code and Servlet is failed to attract the programmer.
To overcome the problem with Servlet technology we use jsp technology.
A JSP page contains both html tags and JSP tags. Html tags will produce static output and JSP tags will produced dynamic output. Because of JSP tags we called as JSP is dynamic web page.