The Project Browser is a dockable window, which lists all sheets/models in the currently opened file.
The Sheets/Models palette lists all sheets and models in the multi-sheet file. The label at the top of the palette indicates the file currently open in Autodesk Navisworks. The sheets/models can be represented as a list view or a thumbnail view. By default, the display order is the same as in the original file. The currently selected model/sheet is indicated with a shaded background, and the model/sheet currently opened in the Scene View is indicated with a black graphic border. When you open a multi-sheet file, not all sheets/models may have been prepared to be used in Autodesk Navisworks. The sheets/models which require preparation are indicated with the Prepare 
icon.
You can select several sheets/models at the same time with the SHIFT and CTRL keys, but you cannot open more than one sheet/model in the Scene View.
The Properties palette is used to examine properties for the sheet/model selected in the Sheets/Models palette. You can also view the properties for the currently opened file by clicking on its name. The properties are grouped by category, are read-only, and can be expanded/collapsed.