Apache is a free and open-source cross-platform web server software.
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.
OpenSSL is a software library for applications that secure communications over computer networks against eavesdropping or need to identify the party at the other end.
Windows Server is a brand name for a group of server operating systems.