Apache is a free and open-source cross-platform web server software.
Java is a class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible.
Mod_jk is an Apache module used to connect the Tomcat servlet container with web servers such as Apache, iPlanet, Sun ONE (formerly Netscape) and even IIS using the Apache JServ Protocol. A web server waits for client HTTP requests.
Windows Server is a brand name for a group of server operating systems.