As important as it might be to require a word to exist in a search query, it may be just as important to provide words that you do not want to be present in a search.  This is where the NOT operator, or the - (minus) comes in handy.  This often helps visitors remove documents by specifying words that may not have relevancy to their search.  In the example below, the words central and park are required, however, the word mime must not be present in order for a document to show up on the results page.
 
 
 
The same thing can be accomplished with + and - operators in the example below.
 
 

The OR operator, or the | (pipe) is a condition that states that the word or phrase can be present (and thus give it a higher relevancy ranking), but it is not required for a document to show up on the results page. This operator is useful to include additional search query parameters without completely removing other candidate matches.  In the example below, the word search is required, but the word term is not -- however, if it is present in a document, it will score a higher relevancy.
 
 

Searching for phrases means that the words between the quotes must show up in that exact order, adjacent to one another.  In the example below, the complete phrase "Detroit Rock City" must be present in a document in order for it to show up on a results page.  Having the words Detroit, Rock, or City on the document is not enough -- the words must be in the exact word order as provided between the quotation marks.