Search Engines

A Web search engine is a tool designed to search for information on the World Wide Web. The search results are usually presented in a list and are commonly called hits.

The term "search engine" is often used to describe both crawler-based search engines and human-powered directories. These two types of search engines gather their listings in very different ways.

Crawler-Based Search Engines

Crawler-based search engines, such as Google, create their listings automatically. They "crawl" or "spider" the web, then people search through what they have found.

If you change your web pages, crawler-based search engines eventually find these changes, and that can affect how you are listed. Page titles, body copy and other elements all play a role.

Human-Powered Directories

A human-powered directory, such as the Open Directory, depends on humans for its listings. You submit a short description to the directory for your entire site, or editors write one for sites they review. A search looks for matches only in the descriptions submitted.

How can we search better

Boolean AND means that all the terms you specify must appear in the documents, i.e., "heart" AND "attack."  You might use this if you wanted to exclude common hits that would be not be useful for your particular search.

Boolean OR means that at least one of the terms you specify must appear in the documents, i.e., bronchitis, acute OR chronic.  You might use this if you didn't want to rule out too much.

Boolean NOT means that at least one of the terms you specify must not appear in the documents. You might use this if you anticipated results that would be totally off-base, i.e., nirvana AND Buddhism, NOT Cobain.