Today, search engines are sophisticated programs, many of which allow you to search all manner of
files and documents using the same words and phrases you would use in everyday conversations.
It’s hard to believe that the concept of a search engine is just over 15 years old. Especially consider-
ing what you can use one to find these days!
What Is a Search Engine?
Okay, so you know the basic concept of a search engine. Type a word or phrase into a search box
and click a button. Wait a few seconds, and references to thousands (or hundreds of thousands) of
pages will appear. Then all you have to do is click through those pages to find what you want. But
what exactly is a search engine, beyond this general concept of “seek and ye shall find”?
It’s a little complicated. On the back end, a search engine is a piece of software that uses applica-
tions to collect information about web pages. The information collected is usually key words or
phrases that are possible indicators of what is contained on the web page as a whole, the URL of
the page, the code that makes up the page, and links into and out of the page. That information
is then indexed and stored in a database.
On the front end, the software has a user interface where users enter a search term — a word or
phrase — in an attempt to find specific information. When the user clicks a search button, an
algorithm then examines the information stored in the back-end database and retrieves links to
web pages that appear to match the search term the user entered.
You can find more information about web crawlers, spiders, and robots in Chapter 14.
The process of collecting information about web pages is performed by an agent called a crawler,
spider, or robot. The crawler literally looks at every URL on the Web, and collects key words and
phrases on each page, which are then included in the database that powers a search engine.
Considering that the number of sites on the Web went over 100 million some time ago and
is increasing by more than 1.5 million sites each month, that’s like your brain cataloging every
single word you read, so that when you need to know something, you think of that word and
every reference to it comes to mind.
In a word . . . overwhelming.
Anatomy of a Search Engine
By now you probably have a fuzzy picture of how a search engine works. But there’s much more to it
than just the basic overview you’ve seen so far. In fact, search engines have several parts. Unfortunately,
it’s rare that you find an explanation for just how a search engine is made — and that information is
vitally important to succeeding with search engine optimization (SEO).
Search Engine Basics
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