The Columns tab is essentially a checklist where you can choose what Columns of data will display on your report.  You can choose to have as many columns displaying as you'd like at any time. 

• When reporting on a specific record type, you can add columns for any of that record type's form fields.  For instance, in the screenshot below, I've chosen to display columns for Type of Fixture, Number, and Project Cost which are specific to the Gas Permit record type which I've chosen to report on in the General tab. 

• Adding columns is excellent for gathering large sets of data, and when combined with Filters from the Filters tab they help provide very specific data.  For instance, if you only wanted to see records from the screenshot above where the Type of Fixture is Oven, you would go to the Filters tab and choose "Add a New Form Filter," then choose "Type of Fixture is Oven."