Boolean operators are words you can use to combine search terms. The basic operators available to use in academic research databases are AND, OR, and NOT. To get more results, use OR with a related word. To get fewer results, use NOT with a related word that appears in your results but is not relevant to your research question.
If you search peanuts, you will get results that use the word in any way:
NARROWER SEARCH: If you search peanut AND butter (or just peanut butter), you will only get results that have both words:
BROADER SEARCH: If you search peanut OR butter, you will get results that have one or the other or both words:
NARROWER SEARCH: If you search peanut NOT butter, you will get results that have the word peanut but not the word butter:
Learn more about Boolean operators and advanced database searching from the University of California, Berkeley: Basic Search Tips and Advanced Boolean Explained.