Boolean Logic is Algebra that works with logical rather than numeric relationships.
Algebra comes from the Arabic al-jebr meaning "reunion of broken parts" (jebr can be pronounced either gobre or jobre)
Boolean Logic is a form of algebra in which the variables have a logical value of TRUE or FALSE.
AND = Can be thought of as BOTH. It requires that both or all objects (search terms) be present in the results. In online searching AND serves to narrow the search and is used for combining differing concepts.
OR = Can be thought of as EITHER. It is used to find either one term or another. In online searching OR serves to broaden a search and is used to search synonymous or closely related terms.
NOT = Can be thought of as AND NOT. It is used to eliminate records. In online searching it serves to narrow a search. Exercise caution when using the Boolean NOT as needed concepts may be eliminated unintentionally.