Rich Internet applications (RIA) are Web based applications with the ability to respond to client in desktop applications way.
Early Internet applications were built, using only basic HTML as graphical user interface (GUI). These applications do not have the look n feel of a desktop application. Web pages refreshes each time, when user clicks on a link in web page.
The initial internet connections were relatively slow. So these slow internet connections made an new term "World Wide Wait".
Now a days due to existence of high speed internet connections, RIA applications came into existence.