Library Terms
Library catalogs and databases use controlled vocabularies, standardized and organized sets of words and phrases that provide a consistent way to describe data. These are usually applied to subjects or topics of sources, essentially tagging in them in the catalog or database.
Tip: if you find a really good source, look at the subject terms listed in the record and consider using those keyword in your next search. You can also click on a hyperlinked subject to see all the sources in that database that are tagged with that subject.