The fields defined at the 'Result Fields' tab are the fields shown whenever Duplicate Check return results. These fields are also included in the returned record result details after a DC job completion on the DC Results page.
The 'Result Fields' feature works with all objects. You can look up a field in the search box or just scroll down and find it by yourself. When you select a field and then click on the arrow pointing to the right, that field will start to show in the result fields on the DC Job results page.