This dialog appears when you click Menu > Column > Add Formula Fields in the Query Editor. It helps you to add formulas into a query to be columns of the query.
The following are details about options in this dialog:
Formulas
Lists all the formulas available to be added to the query.
Expression
Shows expressions of the selected formula.
Add
Adds the selected formula to the query.
Close
Exits the dialog.
Help
Displays the help document about this feature.