Reference materials are information sources which provide definitive, factual and concrete information. Examples of reference materials include dictionaries, encyclopedias, directories, handbooks, almanacs, indexes, bibliographies, atlases and statistical sources.
Reference articles discuss the foundational knowledge associated with a subject as it has been vetted by the experts in the field. Reference articles may be used to provide background knowledge written for a general audience; to provide a definition of a concept or theory; to get a quick overview of what is widely accepted as authoritative on the topic.