Understanding the relationship of chart, pie, and series
Pie charts are simple to plot; they have no axes to configure and all they need is data with categories. Generally, the term pie chart refers to a chart with a single pie series. In Highcharts, a chart can handle multiple pie series. In this case, a chart can display more than one pie; each pie associates with a series of data. Instead of showing multiple pies, Highcharts can display a donut chart that is basically a pie chart with multiple concentric rings lying on top of each other. Each concentric ring is a pie series, similar to a stacked pie chart. We will first learn how to plot a chart with a single pie, and then later on in the chapter, we will explore the plotting with multiple pie series in separate pies and a donut chart.