Search operators consist of a character or string of characters added to a search engine query which provide for advanced filtering (to narrow the focus of the search) or allow the user to access additional information. Examples:
Exclude word (add hyphen before word): speed -car
Exact match (add parentheses): "medical-surgical nurse"
List of related sites (add "related:" before domain): related:webmd.com
More information about search operators
Comprehensive list of search operators