It is used to narrow a search. The search term used after the AND NOT operator will be excluded from the result. In the examples above the same operator was used in every search, but you can also combine the three Boolean operators. All records found with this query will contain the word police. While some of them will contain the word women and some of them will contain the word children.
Some documents can contain both the words children plus women.
So all the documents in this result can contain either the combination of words police and women or just the word children. When you use the OR operator in combination with other Boolean operators be sure to surround the OR words by parentheses so that they will be kept together as a logical unit. When you want to perform complex Boolean searches always use the parentheses to keep the logical parts of your query together.