A Doughnut Chart is used to show multiple segments across multiple groups. In the image below, we see twelve segments for each year with three years worth of sales presented in a single chart.
Compare this to a Pie Chart where groups are displayed a single group at a time.
As in the other chart formats available in Ninox, hovering the mouse over any single element in the chart will result in the numeric value represented by that segment, along with the name of the segment appear in an on-screen help window.
Since a Doughnut chart can potentially display multiple segments across multiple time periods on the same chart, using the Data Series option to display records as the segmented content results in a graph that displays each period as a ring in the doughnut with each field segment being a component of each ring as demonstrated in the image below.