Every time you make selections in an application, Qlik Sense filters the data, creating a set or group. If nothing is selected, then it means that the whole data model is part of the set.

Set analysis allows you to analyze data different to the set created by your selections. The subset analyzed by set analysis of data could be inside the main dataset or outside.

For example, when displaying in a chart the number of customers by product type for 2018 compared to the total number of customers, set analysis will help get the total out of the selection from 2018.