Overviews are summaries of the information in secondary and primary sources. Encyclopedias and summaries on websites are overviews. They should not be cited in an academic paper!
Is it okay to use Wikipedia for a college research project? Yes, but only as a starting point.
Wikipedia is an excellent starting point. You should use Wikipedia! Read Wikipedia articles, and write down clues that you find, like keywords and search terms. Follow the citations at the bottom of Wikipedia articles. Use these clues to find sources you can cite.
Don't cite Wikipedia.
Don't assume that everything you read on Wikipedia is true. Treat Wikipedia as a collection of valuable rumors. Follow up on each rumor, using trustworthy sources, to see whether the rumor is true.
Secondary sources include scholarly books and articles. Scholarly sources provide analysis of all aspects of a play, including its composition and its production history. Scholarly articles will be especially helpful as you seek to answer the question "Why This Play Now?" for the dramaturg's note.
To find scholarly articles, start by searching in Quest and limit your results to "Peer-reviewed Journals."
It's easy to find scholarly articles about a particular play, but you probably won't find scholarly articles about a particular production of that play. That's okay. Look at the articles about the play, and ask yourself how they might help you write your dramaturg's note.
Quest covers all subjects, not just theatre. If Quest gives you too many irrelevant results, try searching in these two databases, which cover English literature (including plays):
Primary sources are first-hand information about a play and/or specific productions. Including:
You will come across two kinds of primary sources: some will be first-hand information about your play in general, like an interview with the playwright. Other primary sources will be specific to the production you've chosen, like images and cast & crew lists.
Resources like reviews can be both secondary and primary.