If the checkbox, Provide services for Citrix XenApp “desktop” sessions only is selected in the Host Control Panel (default = unchecked), Host instances will only be injected into virtualized “desktop” sessions, and not into virtualized “application” sessions. This will allow administrators to conserve the number of licensed Host instances available on a RDS Server machine.
NOTE: The Host for RDS “Provide services for Citrix XenApp ‘desktop’ sessions only” feature requires the Citrix XenApp WMI provider that is only in Enterprise and Platinum editions of the product; it’s not available in the “Advanced” edition. The WMI provider is required for the Host feature to work, therefore, only the Enterprise and Platinum editions are supported.