Some fields are included in your query only so you can filter or sort based on them. You may not necessarily be interested in seeing that field in the query results. For instance, you may want to limit your query to all dogs born before 8/5/93, but you don't want each dog's birth date to appear in the query.
To exclude a field from appearing in the query results, deselect the check box in the Show row. To include it again, select the check box again.