Combination charts A combination chart uses two or more chart types to emphasize that the chart contains different kinds of information. The chart in the example above shows one data series (Projected) as a column chart type and the other (Actual) as a line. To create this kind of overlay effect, change the chart type for one or more of the data series in the chart.
Secondary axis When the range of values for different data series varies widely, or when you have mixed types of data, you can plot one or more data series on a secondary value (y) axis. The scale of the secondary axis reflects the values for the associated series. The chart in the example above shows the number of homes sold on the left y-axis and the average price on the right y-axis.