This form opens modally when a record to be imported contains an error condition.

The number of fields displayed on the left read-only text box depends upon which fields failed the validation.
To the right of each field is a multi-line text box indicating the reason why the import failed. Scrollbars to the right of the field allow further text to be viewed.
The right-most field is editable and is where the text/value which will replace the original value can be entered/edited.
More: