A data set is a collection of variables and associated data. When you create a data set, you capture a snapshot of the dynamic data that is currently displayed on the artboard. You can switch between data sets to upload different data into your template.
The name of the current data set is displayed at the top of the Variables panel. If you change the value of a variable so that the artboard no longer reflects the data stored in the set, the name of the data set is displayed in italic type. You can then create a new data set, or you can update the data set to overwrite the saved data with the new data.