It can be used as an input method of last resort if you find yourself on a system without a Pinyin input method editor installed. It does not require that your operating system have Chinese support installed or that you have a Chinese font available. If no Chinese font is detected on your system it will prompt you to download the FireFly font for temporary usage. This font is available under the Arphic Public License. The Java runtime, version 5 or greater, is required. Your browser must also have the Java plugin installed.
Depending on the security settings on your system, you may not be able to copy and paste out of the applet window directly. If not, hit the copy button to copy the text into the lower HTML text area and copy the text from there (if you do not have a separately installed Chinese font, the text will not display correctly in the text area). You can also download the text to your local machine by hitting the download button. Be sure to elect an encoding suitable for your content (i.e. don't pick Big5 for simplified text, or GB for traditional text).
For inputting Chinese regularly, you'll probably want to install the Chinese input method support that comes with your operating system. Otherwise, you can download a stand-alone version of this input method. If you already have a Chinese font, you can download from the first link. If you don't have a font and can't install one separately, then download using the second.