Search Engines
A Web search engine is a tool for locating information
on a specific subject.
When you search for information in any Web database,
you use keywords (words or phrases) to identify or
describe the information you are seeking. The search
engine then searches through the Web sites in its
database and returns a list of Web sites that match
your searching criteria. There is no controlled vocabulary or list of standardized
terms or descriptors for the Web. Because there is
no controlled vocabulary, the use of synonyms and
variations of keywords to describe your search query is
very important. (For help on keywords, an online thesaurus is
available).
The operation of each search engine varies. Most
use automatic software programs known as spiders, worms,
robots and gatherers, which roam the Web and collect
URLs or addresses of Web sites to add to their database.
Some examine a Web page and follow each link to other
links. Some search engines are updated daily; others
are not.
Most search engines are free. They obtain their revenue
from advertisers who pay to have their ads or services
placed on the home page of the Web search engine.
Some prominent search engines and their URLs are as
follows:
