Boolean Logic is the use of either AND, OR, or NOT as directed on the How page.

You should use one or more of those three words to connect your keywords 
or phrases when searching the internet.
 
Some search engines have substituted a plus (+) sign 
for "and" and a minus (-) sign for "not." 

These terms can be useful in your search. They can help filter out 
what you don't want and find sources for what you do want. 

Another useful strategy is to put quotation marks around a phrase or name 
("Boolean logic" or "Kevin Henkes") 
when searching.  The search engine will then look for these words or thewhole phrase 
together (instead of coming up with everything having to do with the word Kevin, 
for example).