A reference source is a resource that can give you basic, introductory information on a topic. These include resources like encyclopedias, dictionaries, atlases, and other resources containing reliable basic information about a subject.
How to Use a Reference Source
Reference sources are useful for giving you a general introduction to a topic that you are not familiar with, finding information on basic concepts (like how a scientific process works or general information about a medical condition). Reference sources can also be useful for finding keywords.