Field Settings and Area Settings both allow you to make changes to your data as you process it through Importacular into the Raiser's Edge. They may be either red or green depending upon if setting selections are present.
Field Settings work with specific rows within a mapping. For example, you can see the green radio button at the end of the row for Fund indicating that Field Settings have been selected for that particular field.
You access the Field settings at the end of the row for that respective field. You can read about Field settings here.
Area Settings work with an entire mapping. Below, you can see a gift mapping. Since the settings button to the far right is red, we know that there aren't currently any area settings added to change how this gift mapping is entered into the Raiser's Edge.
You would access Area settings at the end of the row for that Area mapping (in the above image, you would open the Gift Area Settings by clicking on the red button).
For more information regarding the specific functions of Area Settings, please refer to the specific section of the User Guide that relates to the Area that you're mapping in your import.