A doughnut chart is just like a pie chart showing the relationships of segments to a total except that the it also may contain multiple data series. Each ring in the chart represents a data series and the first series is closest to the center of the ring.
The doughnut chart is not a chart that I would recommend, it has the same issues as the pie chart, but also the rings are distorted because of their different sizes. This makes it really hard to compare the parts between rings, data labels must be used. The nature of this chart also makes it not practical to include more than 7 categories, each part becoming smaller and smaller for each category you add.
How to build
Go to tab "Insert" on the ribbon.
Click on "Insert Pie or Doughnut Chart" button.
Click the "Doughnut" button.
Add a second series
Right click on chart.
Click on "Select Data...".
Click "Add" button.
Select the new series values you want to add to the chart.