Definition

Search Engine

 A program that searches documents for specified keywords and returns a list of the documents where the keywords were found… 
src: http://www.webopedia.com/TERM/s/search_engine.html

Types

There are three types of search engines on the Internet:

1. Directory Driven Search Engine – http://www.yahoo.com - Everything is organized based on a directory structure.  Yahoo’s entries are entered by hand and are not crawled.  It is well organized, hence it is popular.
2. Database Driven – http://www.google.com - These search engines crawl the Internet and cache pages on websites into their databases.  You then search their databases when you do a search.
3. Combination Site – http://www.dogpile.com - enter one search request, searches multiple search engines at the same time.

Search engines that crawl, are also referred to as spiders.  Hence, the “web” in World  Wide Web.

A spider

A program that automatically fetches Web pages. Spiders are used to feed pages to search engines. It's called a spider because it crawls over the Web. Another term for these programs is webcrawler.  Src: http://www.webopedia.com/TERM/S/spider.html

Using Search Engines (Google)

Google.com is the largest search engine in the world at the moment, so we will use their help information for this lesson.

Basic Search - http://www.google.com/help/basics.html
Advanced Search - http://www.google.com/help/refinesearch.html
Google Search Results Page - http://www.google.com/help/interpret.html