Background sources are written for a general audience and are intended to give an overview of a topic, fill gaps in the reader’s knowledge, and provide context for deeper understanding. Examples include Wikipedia, introductory textbooks, and reference works such as encyclopedias, dictionaries, and handbooks. They can be a useful place to start your research and can assist in selecting a topic for a research project, locating basic information and key facts, defining important words and concepts, and getting suggestions for additional sources to consult.
Typical characteristics of background sources:
Related Subject Search on Library of Congress Subject Heading
Alternative way to search: Imag(in)ing the war in Japan etc