To use when studying the social sciences, behavioral sciences, and many other sciences.
Books, periodicals, pamphlets, charts, statistics, maps, interviews, television, radio, Internet, online databases, and many other types of material. When credit is properly attributed, you reduce the chance of plagiarizing.
It is not imperative to cite factual, well-documented information (e.g., John F. Kennedy was the President of the United States). However, quotations, statistics, images, and artwork taken from, e.g., books, periodicals, and the Internet, should be cited.
Note: When in doubt, CITE.