From Wendy Boswell,
Your Guide to Web Search.
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Where does the term Boolean originate from?

Boolean searching is built on a method of symbolic logic developed by George Boole, a 19th century English mathematician. Most online databases and search engines support Boolean searches. Boolean search techniques can be used to carry out effective searches, cutting out many unrelated documents.

Is Boolean Search Complicated?

Using Boolean Logic to broaden and/or narrow your search is not as complicated as it sounds; in fact, you might already be doing it. Boolean logic is just the term used to describe certain logical operations that are used to combine search terms in many search engine databases and directories on the Net. It's not rocket science, but it sure sounds fancy (try throwing this phrase out in common conversation!).

Basic Boolean Search Operators - AND

Using AND narows a search by combining terms; it will retrieve documents that use both the search terms you specify, as in this example:

• Portland AND Oregon

Basic Boolean Search Operators - OR

Using OR broadens a search to include results that contain either of the words you type in. OR is a good tool to use when there are several common spellings or synonyms of a word, as in this example:

• liberal OR democrat

Basic Boolean Search Operators - NOT

Using NOT will narrow a search by excluding certain search terms. NOT retrieves documents that contain one, but not the other,of the search terms you enter, as in this example:

• Oregon NOT travel.

Keep in mind that not all search engines and directories support Boolean terms. However, most do, and you can easily find out if the one you want to use supports this technique by consulting the FAQ's (Frequently Asked Questions) on a search engine or directory's home page.