When you first open Impact Explorer, and no elements have been loaded for assessment, you will see the Impact Explorer logo, with menus and buttons along the top edge of the window. (You can choose your own logo for display here if you want - see the Background settings dialog.)
This is the main Impact Explorer screen. When nothing else is happening, this is what is displayed. When you start to use the software, for example running an activity, the appropriate windows will appear in place of the logo.