Reference texts, like encyclopedias, directories, and dictionaries, can be starting points for research on a person or topic. Wikipedia is a good example of a 'reference source'. It has a little bit of information on a great many topics, but doesn't go into much depth on any topic.
Reference sources are often used primarily for 'background information', rather than as final sources. Often times, reference sources will be 'library use only', but they are still valuable resources.