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 citation on the results list page.
To restrict results to a particular type of document, perform a Basic or Advanced Search. Then from the results list page, click Expand/Limit and select the type of document from the Article type limiter.