A VividCharts chart is a single visual that lives under a VividCharts dashboard record. A chart can be thought of as an individual report that has its own set of conditions and settings. When a chart is defined and created, you will then need to add it to your Service Portal page by selecting the corresponding chart widget.
You are also able to create custom chart collector scripts to give you full control over how you are getting the data out of your ServiceNow instance. This can be extremely useful if you need to pull data from multiple tables or want to run a particular set of calculations against the table that can’t be handled with out-of-the-box charts or reports.