Annual Reviews is a database of literature reviews in many subjects. These give you information about the big issues at the time of the paper, core and cutting edge references that everyone in the field reads, and suggestions for future studies. You can also see newer papers that cite these literature reviews.
Articles chop up your topic into little, narrow questions. If you find 5 articles, each presenting a narrow study, it's often hard to see how they fit together and what question they are all trying to answer.
Encyclopedia articles and books can give you overviews of your topic and lead you to the important questions asked by researchers. Subject specific encyclopedias contain articles written by experts in their fields and should put your idea or question into a historical, research, or social context. They will also lead you to further references.