Boolean operators, it uses the word "and","or" and "not" with keywords to control the search. For example if you search for health and food, the search engine will give a narrow search focusing on the two keywords. Using "or" with keywords will give much broader results. Using a "not" will remove one keyword from the search, ex. windy not rainy will give results of the keyword windy only. An asterisk on the other hand, gives wider results with variations.
