The technique most database search engines use comes from the symbolic logic system developed by a 19th-century mathematician named George Boole.
Boolean searches use a basic syntax made up of operators and search terms.
You thereby avoid pulling up documents you have no use for, like the website for Judy Garland or documents about plain old ordinary orange sherbet. Ami-Pro OR Amipro Terms combined with OR bring up anything that matches one of your terms. This is the default operator for most Web searchers. It increases your total number of hits, and though you may get some irrelevancies, it's a good operator to use. Boolean allows you to combine operators.