Rich Internet Applications (RIAs) are web applications that have most of the characteristics of desktop applications, typically delivered either by way of a standards-based web browser, via a browser plug-in, or independently via sandboxes or virtual machines. Examples of RIA frameworks include Ajax, Curl, GWT, Adobe Flash/Adobe Flex/AIR, Java/JavaFX,Apache Pivot, Mozilla's XUL, OpenLaszlo and Microsoft Silverlight.
Such web applications have characteristics of desktop applications. Rich Internet applications (RIAs) offer a rich, engaging experience that improves user satisfaction and increases productivity.Using the broad reach of the Internet, developers can deploy RIAs across browsers and desktops. RIAs differ primarily from other Internet applications in the amount of interaction in the interface. A traditional page-based Internet application limits interaction to a small set of standard controls such as checkboxes, radio buttons, form fields and buttons. This severely limits the ability to build usable and engaging applications, and most Internet applications have proven clumsier and more difficult to use than their desktop counterparts.
Flash is a state of the art technology that caters to both design and programming aspects of a Website. In other words, both static and dynamic Websites can be created using Flash design and programming, without having to rely on any server side scripting languages like ASP.net , PHP etc.
Flash is a complete solution in itself. It provides an interface to the designers which enables them to experiment with and achieve various possibilities of effective animations through inbuilt functions. On the programming front, Flash developers can create interactivity in Flash designs through guage that is specific to Flash programming. The scope of what can be achieved with Flash design and programming is amazing. You could have Flash animated logos, Flash shopping carts, Flash audio and video players and so on.