A typical use case for SuperCache is a user reading a Word document. When the user scrolls down the document, SuperCache is able to detect areas in the document that have just moved up. Instead of resending those graphics to the end point, the end point renders already cached graphics providing a significant bandwidth reduction between the virtual desktop or application and the end point.

SuperCache is crucial to deliver a great user experience over WAN. On LAN scenarios, SuperCache improves the server scalability and user interactivity by reducing the amount of data pushed through the network and processing required on the client. SuperCache is available in both XenApp and XenDesktop. It is enabled by default and requires no configuration from the administrator.

The following video compares the user experience when SuperCache is on vs. off.

Source:http://community.citrix.com/blogs/citrite/juanr/2009/08/18/HDX+Learning+Series+-+SuperCache