Databases use Boolean operators to narrow or broaden searches to specific topics. The most common Boolean operators are AND, "quotations", OR, NOT. Here is an example of an Advanced Search box. The operators are in dropdown menus or you can type them into the search boxes themselves.
AND
Narrows your search
Eg. perception AND “actor-observer effect”
OR
Connects like terms
Eg. teens OR adolescents OR “young adults”
“preoccupied attachment” OR “anxious attachment”
NOT
Removes certain articles from search results
Eg. flight NOT birds
" " Quotation marks
Search an exact phrase
Eg. "multiple personality disorder"
* (asterisk)
Can open search to all possible endings of a word
Eg. communic* for communicators, communicating, communication