This component can be used to add a metadata description for a field derived or calculated in a view e.g. "select field1+field2 as myfield from table".
An existing example of a derived data field that is defined in meta only is the field case_color. Case_color is defined in the view vListCases but does not exist in the physical table cases.
Make sure that you define the field carefully using the correct table prefix in the field name and that you do not try and use a field name already used e.g. pers_fullname.