Processing dynamic pages
When a web server receives a request for a static web page, the server sends the page directly to the requesting browser. When the web server receives a request for a dynamic page, however, it reacts differently: It passes the page to a special piece of software responsible for finishing the page. This special software is called an application server.
The application server reads the code on the page, finishes the page according to the instructions in the code, and then removes the code from the page. The result is a static page that the application server passes back to the web server, which then sends the page to the requesting browser. All the browser gets when the page arrives is pure HTML. Heres a view of the process: