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What Is A Search Engine?

Search Engine Defined

A search engine is a mechanism for locating information on the World Wide Web (WWW) by allowing a user to enter queries. The program responds with a list of matches from its database. A relevancy score for each match and a hyperlink to the URL are usually returned. Each search engine uses a different method to determine which sites to list first when you do a search, which is why results can vary so greatly. Search engines create a database of sites using robots which are referred to as spiders, which are indexing programs that search for keywords within a title or text of a web site. You can search the database by entering words or phrases and the search engine returns a list of hits that matches your request. Factors that influence results include the size of the database, frequency of updating, the research capabilities of the robots and the options of a given search engine. Because the Internet is always growing and the fact that each search engine has different capabilities, performing the same search using different search engines will often give you a huge array of results.



Closely related to a search engine, a directory is a hierarchically organized index that allow the user to browse through lists of web sites by category or subject. They are selective databases compiled by human indexers who regularly review the WWW and categorize new web sites.  The top level of a directory's hierarchy provides a broad range of very general topics such as art, computers, entertainment, etc.  Each of these broad topics are hyperlinks to more specific topics, such as graphical ( a form of art), Macintosh (a type of computer), movies (a form of entertainment), etc.  By simply clicking on the category for the topic in which you are interested, you continue to move down through the hierarchy, selecting subcategories and narrowing the search at each level, until you are presented with a list of hyperlinks that pertain to your topic.  Yahoo is an example of a directory.


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Technical Terminology Of Search Engines
Boolean Expressions/Queries Mathmatical expressions used in a search query to help narrow a broad topic.  They use the operators AND (+), OR, and NOT (-). 
Query Syntax A set of rules describing what makes up a legal query.  On some search engines, special symbols may be used in a query.
Query Information entered into a form on a search engine's Web page that describes the information being sought.  Note that a query is not usually phrased as a question.
Hyperlink Text and/or graphics on a Web page that will cause the browser to retrieve and display another Web page or graphic.
Hit A URL that a search engine returns in response to a query.-
Match A synonym for hit.
Metasearch Engine A search tool that calls on more than one other search engine to do the actual searching simultaneously.  Also referred to as All-In-One-Search Engine.
Relevancy Score A value that indicates how close a match a URL was to a query; usually expressed as a value from 1 to 100 (in percentage %), with the higher score meaning more relevant.
Evaluator The function that assigns relevancy scores to the information retrieved.
Gatherer The indexer (human) or program (robot) that transverses the WWW collecting information about web pages.
Indexer The human or function (program, robot) that categorizes the data obtained by the gatherer. 
URL Uniform Resource Locator:  aka..A web page address such as,


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Description Of Some Popular Search Engines & Tips


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A combination of a search engine and directory service.  Contains a section with links to Frequently Asked Questions (FAQ's), email addresses, current news and company listings. 

  • Use commas (,) to separate phrases
  • Hypenate words that need to be next to each other
  • Put a minus (-) sign in front of a word to exclude it from the search and use a plus (+) sign to require that a word appear in all hits from the query.
  • Capitalize all proper nouns (names, places such as Nicolas Cage or Seattle) and include commas between full names or the engine will look for something like "Bill Gates Seattle" as a single name.


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Considered by many to be the premier search engine, AltaVista is one of the largest and most comprehensive search engines.  Fast and excellent for unclear and hard to find subjects.  Provides both simple and advanced search screens. 

  • The Boolean operator "or" is the default setting beteen words in a query
  • Enclose phrases in quotation marks
  • Attach a "+" in front of word or phrase that is required.   There must not be a space between the "+" sign and the term. 
  • Use an asterisk at the end to truncate (shorten) a word or phrase.
  • Has an advanced search screen with an option to restrict to certain formats of documents returned from query search.  To use this feature, enter a name (title, image, URL), then a colon (:) followed by the search terms.


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A rather colorful screen with pull down menus and buttons make this site an attraction to young people.  It is a top-rated search engine with first-rate speed and advanced search features that gives the user the ability to limit searches to web pages that contain specific files such as Javascript, images (.jpeg or .gif) or sound files.

  • Enclose phrases in quotation marks.
  • Feel free to type in any letter case (ie.."A or a"), it's insensitive.
  • If searching for a person, keep in mind Hot Bot will return results based on several different combinations of a name.
  • Use the selection boxes to limit your search by date, location, file, or by a specific technology such as Java or Javascripts.




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Yahoo, Yet Another Hierarchical Officious Oracle, is the most widely used and consistently highly rated Internet directory.  It is a list of web sites submitted by humans and sorted into categories by indexers comprehensive listings which are updated daily which contributes to its popularity. Current news, stock quotes, sports scores, city maps, regional Yahoos, and resources for kids are available.  

  • After keywords are specified in the query box and submitted, Yahoo will sort the results in four areas entitled: Yahoo Categories, Yahoo Websites, Yahoo's Net Events & Chat, and Most Recent News Articles.  If no matching Categories and Sites are found, Yahoo will automatically perform an AltaVista search. 
  • Enclose phrases in quotation marks ("x").
  • Attach a "+" sign in front of a required word or phrase in search results.
  • Attach a "-" sign in front of words that must not appear in search results.




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Webcrawler is an example of a meta search engine that searches many other serach engines simultaneously once a query is submitted.  Some of the search options include: search any of the words, search all of the words, or search as a phrase.  The engine's search results return titles of documents/web page names   by default only, however there is a Select Summaries option on Webcrawler's homepage which allow you to get more information about the search results.
  • Enclose phrases in quotation marks.
  • Attach a "+" sign in front of required words or phrases.
  • Attach a "-" sign in front of words that must not appear.
  • Webcrawler's Boolean features are very useful, use them if possible.




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Other Resources To Using Search Engines

Here are some more useful references and guides to using search engines.  Those marked with an asterisk were consulted are used for the creation of this webpage. 

Web Resources:


Print Resources:







Main | What Is A Search Engine? | Technical Terminology | Popular Search Engines | Other Resources


Copyright Adrienne Arthur.  Last Updated May 6, 1999.