A Rich Internet Application is not an application that relies on video or state of the art graphics. A rich internet application is like a computer program but on the internet. But no only that it has to have some backend databasing involve. For example, ebay is a rich internet application or other web applications that allows interactivity between the user and the application. I'm not sure if that's a good short summation of it. HEre are a few links that may help you.