Encyclopedias, dictionaries, and other reference resources help you to discover basic information—names, dates, definitions, summaries, etc. These are good places to start when beginning research on an unfamiliar subject, and when choosing or narrowing a paper topic.
Reading a story, memoir, or essay that's set in a country that's unfamiliar to you? Reference works can help you quickly learn enough about a country's recent (or even older) history to help you better understand the context of the text you're reading.
Come across a word that is new to you and can't quite figure out what it means based on the context of what you're reading? It's easy to look it up! Some dictionaries and definition sources that can help:
Interested in consulting specialized reference works for other subject areas? See the library's Subject Research Guides. There's one for every subject taught at Mount Holyoke and most of the guides have a Background Info page listing subject-specific reference works.