Boolean operators is a fancy term for using the words "and," "or" and "not" to connect your search terms. Here is what they do:
AND forces your results to include all of your search terms. It makes your search narrower and more specific. Some databases and search engines automatically assume "and", but some do not, so include "AND" to be on the safe side. If you are not getting enough hits, you could try experimenting by deleting some of your less important terms.
example: education AND technology drugs AND violence AND Mexico
OR means that any of the terms can exist. The result must include at least one of your search terms, but doesn't have to include them all. This is a good way to include different spellings or other terms with the same meaning (synonyms). Just remember that "or" gives you more. example: adolescents OR teenagers OR juveniles OR youth theater OR theatre television OR TV
NOT helps you eliminate terms that you do not want.
example: heart NOT lung high school NOT elementary
Some search engines use the minus sign instead. Example: jaguar -car (so your results will not include the car, but will include the cat)