The properties of the collectionField object are the fields (or categories) used by the collection. The text property (see below) is the (display) string the user sees in the user-interface with viewing a listing of the files files in the collection. Use the collectionField object to set the order the fields are listed in the user-interface, the sort order of the listing of the files, or to set a field as read only.
The collection field values for embedded files in the collection can be got or set through getFieldValue and setFieldValue methods of the Data object.