Text entered in Predefined Value will appear in the element’s text field as long as there is no other value saved in the field. Unlike the Placeholder property, this value will actually be saved with the response on submittal if the user does not change it. Predefined Value is meant to be used when there is a particular value that the great majority of responses will have. This saves the users some time and typing.
Predefined Value set in Edit mode
Predefined Value displayed to user