Building context (and recognizing when you need more context) is an important element in the research process. Tertiary sources, especially subject encyclopedias, are often the best place to start when you are trying to establish some basic historical, social, or cultural context.
Articles in subject encyclopedias are written by scholars who have deep specialization in the topic and the articles themselves go through a stringent editing process. You usually can expect to find the following important information in articles in subject encyclopedias:
The subject encyclopedias listed here are good starting points, but you also should explore the entries in the online collections.
Not sure where to look? Each of these online collections will introduce you to a wealth of dictionaries and encyclopedias.