The CHARTJS component renders charts on client side using the chart.js framework, see: https://www.chartjs.org/

In this framework charts can be flexibly drawn by passing a JavaScript configuration object. Within the CHARTJS component this JavaScript object is assembled on server side as JSON string, which is passed to the client side, converted into an object and then used to configrue the component.

Using the component means that you should take a look into chart.js as framework as well, in order to get to know how to properly configure a chart.