For the legacy AdWords Reports, the fields available for each report are listed in three groupings: Segments (used to group metrics), Attributes (settings or other fixed data) and Metrics (numerical performance data).
When you select a report, the default fields will be selected for you (listed at the right). You can add or remove fields from this list as desired.
Note that the display name for each field is shown, consistent with the web interface, and they are listed in alphabetical order. The list of available fields varies depending on the report your selected.
Select from the list at the left and double-click the field name, or click the [ >> ] button to add the field name to the selected list at the right.
Your report results will be sorted based on the order of the columns, with the first column sorted in ascending order, then the second column, and so on. To reorder the list of fields, simply drag and drop them in the list at the right.