The term document in Gale Virtual Reference Library refers to any entry (article) from an eBook.
You'll find many kinds of documents in Gale Virtual Reference Library, such as Biography, Chronology, Definition, Introduction, Movie Review, Primary Document, and Topic Overview, to name a few. You'll see the document type to the far right of each item on the results list page.
To restrict results to a particular type of document, perform a Basic or Advanced Search. The Search sidebar on the results list page allows you to refine your search. Select the type of document from the Article type limiter.