By default the search engine tries to locate pages which have exact matches for all of the words entered in your search query. If that fails, it then tries to locate pages which contain any words in your search query.
In addition, there are several ways to modify the default search behaviour.
The search engine supports three types of phrase search.
If a query word has a * all words on a page which contain that query word will match.
If a query word contains a ? any character will match that position.
You can use the following boolean operators in your search: AND, OR, NOT. These
operators MUST be in capital letters.
Example: (contact AND us) OR (about AND us)