Go Back replaces the current help topic with the
  preceding help topic. It is possible to step back
  through all the help topics you have seen.

  Stepping back through previous topics in this way can
  also be achieved using the Go Back button, which has
  exactly the same function as this menu item, or by
  using the History... menu item from the Search menu.

  Both these methods can be quicker than using this menu
  item, particularly if you want to go a long way back.