Question

what is a Boolean operator

Answer 1

Boolean operators define the relationships between words or groups of words.

http://aide.eureka.cc/pdf/operateursEkEnCa.pdf

Answer 2

"Boolean Operators are simple words (AND, OR, NOT or AND NOT) used as
conjunctions to combine or exclude keywords in a search, resulting in more focused and
productive results."

Answer 3

Boolean operators are not specific to searches involving words. In fact, Boolean operators come from a algebra. More broadly, they are used to define/describe relationships among and between sets.