In addition to the fields extracted from the data source, system fields are also produced by Qlik Sense. These all begin with "$" and can be displayed like ordinary fields in a visualization, such as a filter pane or a table. System fields are created automatically when you load data, and are primarily used as an aid in app design.
Available system fields
The following system fields are available:
Using system fields in a visualization
System field data is associated. For example, if you add two filter panes, one with $Table and one with $Field, if you select a table, the $Field filter pane will show the fields in the selected table as possible values.
System fields are not included in field lists in the assets panel or in the Expression editor. If you want to use a system field, you need to reference it by typing it manually.
Example: In a dimension in the assets panel
Example: In the expression editor