The HTML page describes the research topic, is specific to the research project, and can usually be automatically derived from the author's preferred text file format (e.g. a LATEXfile).
The Java applet tag embeds the reproducible result in the HTML file. When the HTML page is viewed by a Java enabled browser, the applet tag instructs the browser to download and execute the Java program ReFig.class. The browser finds the Java program relative to the codebase directory at the computer serving the document. The Java program is an applet since extends the Java applet class. Only applets can be executed by a browser.