How Search Engines work

Internet search engines are special sites on the Web that
are designed to help people find information stored on other
sites. There are differences in the ways various search
engines work, but they all perform three basic tasks:

* They search the Internet -- or select pieces of the
Internet -- based on important words.
* They keep an index of the words they find, and where they
find them.
* They allow users to look for words or combinations of
words found in that index.

Early search engines held an index of a few hundred thousand
pages and documents, and received maybe one or two thousand
inquiries each day. Today, a top search engine will index
hundreds of millions of pages, and respond to tens of
millions of queries per day.