Java is a machine language that allows the web site or host to perform just about any task. Java is used to automatically put the browser to full screen or have a text or graphic follow the mouse, like on the Main Page. It's also used in guest books and other cell type systems. Also tracking and special effects.
Java script is a very complex system of tags that are imbedded in the HTML language. Some editing is possible but, if the slightest tag or line is out of place, the effect will not work or might give an error.
To see what java looks like from a designer's point of view, go to the Main Page, right click and choose "View Source". You will see the script between the <script> and the </script> tags.
More and more sites are using java and browsers are scrambling to keep up.