Yes: Turns on the controlled vocabulary feature.
A controlled vocabulary defines a list of valid terms that can appear in metadata fields within CONTENTdm. Enabling a controlled vocabulary for a particular field helps ensure consistent metadata entry and it allows multiple-word phrases to be searchable when browsing by that field. The list of valid terms could be Library of Congress Subject Headings, Thesaurus of Graphic Materials Subject Headings, the contents of already-entered records in that collection, or any other vocabulary specific to a given discipline. Controlled vocabularies assure that spelling and usage is consistently applied within a collection.
(The UW Libraries uses the contents of already-entered records as the basis for our controlled vocabularies. We use the feature most often for subject fields. Catalogers consult the Library of Congress Subject Headings and the Thesaurus for Graphic Materials when entering data. We mainly use ControlVoc after data entry to enable phrase searching.)