imagine the World Wide Web as a network of stops in a big city subway system.
Each stop is its own unique document usually a web page, but sometimes a PDF, JPG or other file. The search engines need a way to “crawl” the entire city and find all the stops along the way, so they use the best path available links.
“The link structure of the web serves to bind all of the pages together.”
Through links, search engines’ automated robots, called “crawlers,” or “spiders” can reach the many billions of interconnected documents.
Once the engines find these pages, they next decipher the code from them and store selected pieces in massive hard drives, to be recalled later when needed for a search query. To accomplish the monumental task of holding billions of pages that can be accessed in a fraction of a second, the search engines have constructed datacenters all over the world.
These monstrous storage facilities hold thousands of machines processing large quantities of information. After all, when a person performs a search at any of the major engines, they demand results instantaneously even a 1 or 2 second delay can cause dissatisfaction, so the engines work hard to provide answers as fast as possible.
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