Java Servlets, JSP, Tomcat
Java Servlets are special Java classes that can integrate with an enhanced web server and enable you to dynamically generate web pages by executing Java code - effectively running your code "inside the web server".
Tomcat is such an enhanced web server (strictly a servlet engine) which you can use here at DoC.
For a basic introduction to all the concepts involved, see our:
How's it setup here at DoC?
We provide Personal Tomcat.