Mouse the mouse over the red dots, the tree, and the house on the top.
When you mouse over them, the cursor changes into the 'help' cursor.  
If you left click on the hotspots, a help bubble will show up.

The house on the bottom is a regular link (if you click on that one, it will take you back to the tutorial). 
This shows that regular links can also works.  

View source and examine the <area> tags.  Each <area> tag has an associated onMouseOver, onMouseDown, and onMouseOut event handler.  

<area shape=CIRCLE COORDS="52,21,17"

  onMouseOver="javaScript:alterCursor('myImage', 'help');"

  onMouseDown="javascript:showPopup(event, 'linkPopup', 'Jim\'s House');"

  onMouseOut="javaScript:alterCursor('myImage', 'default');