This value is used in order to limit, to a subset, the list items shown in the weblet. If a listname property is provided the associated field must be specified in the selector_field property. If the items property designer has been used to define the list of values the corresponding selector value entered in the designer is used.
Single-quoted text or a numeric value. A field, from the working list nominated in listname, can be selected by clicking the corresponding dropdown button in the property sheet.