You can create extensions to the user interface layer of the vSphere Web Client that add GUI elements that are specific for your vSphere environment.

The vSphere Web Client user interface is based on a modular Flex application, hosted on the application server, that runs in the Web browser. The user interface layer contains every visual component of the application, including data views, portlets, and navigation controls.

You can add new features or elements to the Flex application by creating user interface extensions. A Flex user interface plug-in module contains one or more extensions, which add Flex GUI elements to the vSphere Web Client user interface.