Boolean logic consists of three logical operators:
OR, AND, NOT
OR logic collates the results to retrieve all the unique records containing one term, the other, or both. The more terms or concepts we combine in a search with OR logic, the more records we will retrieve
The more terms or concepts we combine in a search with AND logic, the fewer records we will retrieve.
A few Internet search engines make use of the proximity operator NEAR. A proximity operator determines the closeness of terms within the text of a source document. NEAR is a restrictive AND. The closeness of the search terms is determined by the particular search engine. Google defaults to proximity searching by default.
NOT logic excludes records from your search results. Be careful when you use NOT: the term you do want may be present in an important way in documents that also contain the word you wish to avoid.