Go Back replaces the current help topic with the
  preceding help topic. You can step back through the
  help topics you have seen by repeating the Go Back
  operation.

  You can also step back through previous topics by using
  the Go Back button or by choosing the History... item
  on the Search menu. Both these methods can be quicker
  than using the Go Back menu item, especially if you
  want to step back through many topics.