Reference works -- like encyclopedias, handbooks, and dictionaries -- provide great overviews and background information.
In short, reference works are a great way to begin your research.
Need to look up a name, place, term, or event? The sources below contain many different kinds of encyclopedias and dictionaries and are excellent starting points for getting an overview on your topic as well as possible search terms to use later. Try them.
International Encyclopedia of Media Studies
The International Encyclopedia of Media Effects
The International Encyclopedia of Digital Communication and Society
The International Encyclopedia of Political Communication
The International Encyclopedia of Intercultural Communication
The International Encyclopedia of Communication Research Methods
Handbook of Media and Mass Communication Theory