1.  What is Nautilus ?

  Nautilus is an open-source file manager and graphical shell being
  developed by Eazel, Inc. and others. It is part of the GNOME project, and its
  source code can be found in the GNOME CVS repository. Nautilus is still in
  the early stages of development. It will become an integral part of the
  GNOME desktop environment when it is finished.