Rich Internet Applications(RIA) are a cross between web applications and traditional desktop applications, transferring some of the processing to the client end.
run in a web browser, not requiring installation.
run locally in a secure environment called a sandbox
can be "occasionally connected" wandering in and out of hot-spots or from office to office
The term "Rich Internet Application" was introduced in a Macromedia whitepaper in March 2002
Overview - Rich Internet Applications Tool
Engineering Rich Internet Applications