You can view a module, or preview it. What the difference?
When Viewing a module it will behave normally. When Previewing a module a module, it will appear to behave normally, but cannot be completed, cannot be marked done, will not apply points, etc. The most common way to Preview a module is to click the (you guessed it) Preview Module button.
However, you should note that if you copy the full URL of the preview, that Preview Mode will be active wherever you use that link.
You can tell if you are in preview mode if the URL of the module ends in "&preview=true," such as:
To exit Preview Mode, or to use a link to a module not in Preview Mode, simply delete the end of the URL, so that it would end just before the ampersand, like this: