We have two clients for QlikView: The C client (fat client, written in C++) and the Ajax client (java script and xml). You probably mean the difference between the two, because by default the C client is used for development andthe Ajax client is used in web situations.
However, if you turn on WebView in QlikView Desktop, you will develop using the Ajax client. Then you will see exactly what an Ajax user will see. You can toggle the Desktop between the two modes.
Further, if you install the QlikView plug-In, and enable usage of it in the QlikView Management console, you can view the app with the C client.