XBAP is a WPF application that runs inside the browser of Web pages.
The application of HVAR is a full-fledged WPF application, which has some major differences:
The HVAR application runs inside the browser window and can occupy the entire area of the Web page or only a part. (In HTML, it is marked with the <iframe> descriptor.) The HVAR application has limited rights to use a lightweight deployment model that allows users to run WPF applications without the risk of executing potentially dangerous code. The XBAR application is granted the same permissions as the .NET application that is launched from a global or local network, since a similar security mechanism is used. The HVAR application does not require installation (a special installation on the user's computer). When you start the HVAR application, it is loaded and placed in the browser's cache, but not installed on the system. This gives the instant-update Web model-every time a user accesses this application, a new version is downloaded (if it is not in the cache and has been updated).Unlike the software model used in ActiveX and Silverlight technologies, where applets are actually loaded inside the browser process, XBAP applications only display their content in the browser window, but like any WPF application, they are launched as a separate process controlled by the CLR.