This sample illustrates Facebook users in a chart for different countries over several years. In a line-based series, data points can be annotated using symbols.
Each points in a series can be represented as a symbol through marker. We can also customize the shape, size and color of a symbol through marker properties.
Tooltips are enabled in this example. To see a tooltip in action, hover over or tap on the chart.
More information on the marker can be found in this documentation section.