This window, which is accessed using Window > Preferences > Perforce QAC, displays the location of the Perforce QAC installation that is currently being used with the Perforce QAC Eclipse.
This display is especially useful if multiple versions of Perforce QAC have been installed, and an environment variable is being used to switch between the versions of Perforce QAC being used with the plugin (please refer to the Perforce QAC Eclipse Installation Notes).