You can choose among a variety of methods to move
  around in and view the namespace.

  To scroll through the namespace, you can use horizontal
  and vertical scroll bars and stepping arrows.

  You can use the index window to show the name where
  the slider is currently positioned in the namespace.
  To display an index window when in outline format, drag
  the slider up and down the vertical scroll bar.

  When the display is in tree format, you can use the
  navigation window to move around. The navigation window
  contains a reduced image of the currently expanded part
  of the namespace. When you drag the slider on a scroll
  bar while the display is in tree format, the navigation
  window appears. A rectangular box containing the
  portion of the namespace where the slider is positioned
  appears inside the navigation window. Release MB1 to
  display that portion of the namespace in the Browser
  window.

  Another way to navigate the namespace is to select a
  virtual root, which is a directory other than the root
  at which you want the Browser to start displaying the
  namespace. The virtual root is a convenient way to
  focus immediately on a particular directory of interest
  instead of expanding directories level by level. To set
  a virtual root, see the Customize menu.

  In namespaces that are larger than the length of the
  window, scrolling through directory levels produces a
  reference line toward the top of the window.

  The reference line orients you by showing the full
  directory path from the current name to the root. It
  also indicates that you have scrolled past other parts
  of the namespace that are no longer displayed.