AND will make your search MORE SPECIFIC.
Search results will include all of the keywords you link together by the word AND.
Beyonce AND lemonade = information related to Beyonce's Lemonade
OR is MORE.
OR will make your search broader.
Search results will include any of the keywords you link together by the word OR. Sometimes search results will include only 1 of the keywords, sometimes both. This OR That, you aren't being picky.
Beyonce OR lemonade = the Lemonade album, Minute Maid lemonade, lemonade herbal extracts
In the Beyonce example OR is not terribly helpful. OR is great for synonyms, though.
teenager OR adolescent
NOT will make your search more specific.
Search results will exclude mention of the keyword after NOT.
Beyonce NOT lemonade = no mention of the Lemonade album
In addition to "phrase searching," Boolean operators, and truncation you can also use wildcard searches.
Like truncation, wildcard searches will expand your results. The symbols below replace letter(s) that would make up a word. It's like a shorthand way of typing every possible word that fits the pattern with OR in between. Not only will this save you time, but it may give you alternative keywords you had not yet thought of.
|Symbol||What it does||Sample search||Instead of typing|
|*||replaces zero or more letters at the end of a word
(this is truncation)
|comput*||computer OR computing OR computational OR...|
|#||replaces at most one letter||ne#t||net OR neat OR next OR nest OR...|
|?||replaces only one letter||b?t||bat OR bet OR bit OR bot OR but OR...|
Some databases may use these differeny symbols entirely or the above symbols in a different way. Check the database's FAQ section to ensure proper use.
For information that you may not be able to find in a database, check out this how to document on searching in Google (like a pro)