Introduction To Search Engines

Search engines operate by storing and retrieving information about many webpages. This information is gathered by automated programs, called crawlers or spiders, which follow any link they encounter.

When an automated program arrives at a web page it analyzes the contents of that page to determine how it should be indexed. Next the automated program stores information about the web page in an index database. Googles stores part of each of the original web pages as well as information about the web pages. When a Google user searches for cream cheese the term cream cheese will be on the web pages listed in the search results.

When the search engine user enters  the phrase to be searched, called a query, the search engine checks it's index database and provides matching web pages.

Ideally, a search engine will provide relevant results. There may be millions of web pages that include the phrase being searched for, so the search engine ranks the results to provide the most relevant results first. Search engines operate on a combination of algorithmic calculation and human input. An algorithm is a method for solving a problem using a finite sequence of instructions. 

Search engines are usually commercial ventures supported by advertising revenue. Some allow advertisers to pay to have their listings ranked higher in search results. Others make money by running ads alongside the search engine results.

Tom Jacoby