A search for data that meets several criteria by using the Boolean operators AND, OR and NOT (see Boolean logic). For example, the request: "Search for all Spanish and French speaking employees ...

Boolean logic: The method used to evaluate conditions, returning either TRUE or FALSE. Logical functions: The primary logical ...

But it's Boolean logic, or Boolean algebra, for which he's known today. The concept goes far beyond the and and or operators most of us have learned to use in the "advanced" options of search engines.