Guides
Guides are vertical or horizontal lines or areas which can be added to the chart. In this example guides were used to create vertical (darker) area and horizontal areas filled with colors.
Another usage of guides can be found in Stacked 3D column chart example - the average line is a guide.
You can use guides to show value ranges, trend lines, averages, mark events on category axis, etc.
Labels can be displayed next to guides and longer texts can be shown in roll-over balloons too.
