Boolean Operators are things like AND, OR, NOT, and the use of "quotes" around a search phrase. Examples look like:
-"high school students" OR teenagers OR adolescents AND technology NOT Facebook
I am telling the database that I want to find results that include my first three terms and technology, but I do not want articles including Facebook.
Watch the two videos below (Part I and II) from McMaster University on how to use Boolean Operators effectively.