search engine optimization

Explanation of how do Search Engines Work?

If you are getting ready to embark on your Internet Marketing journey you must know how the search engines work!

1. Crawler-Based Search Engines

The big 3 search engines, (Google, Yahoo, & MSN) are known as crawler-based search engines. Crawler-based search engines have three major elements. First is the spider, also called the crawler. The spider visits a web page, reads it, and then follows links to other pages within the site. This is what it means when someone refers to a site being “spidered” or “crawled.” The spider returns to the site on a regular basis, such as every month or two, to look for changes.

How do search engines work with the spiders? Everything the spider finds goes into the second part of the search engine, the index. The index  is like a giant book containing a copy of every web page that the spider finds. If a web page changes, then this index is updated with new information.

Search engine software is the third part of a search engine. This is the program (also known as the ranking algorithm) that sifts through the millions of pages recorded in the index to find matches to a search and rank them in order of what it believes is most relevant.

2. Search Engine Ranking Algorithms

All crawler-based search engines use a ranking algorithm to rank sites for any given keyword. The ranking algorithms of the major search engines can consist of hundreds of factors. However, for purposes of simplicity, rankings algorithms consist of two critical components: 1) Document Analysis and 2) Link Analysis.

In document analysis, search engines look at whether the search terms are found in important areas of the document – title tag, meta tags, heading tags, and in the body of the text.

In link analysis, search engines not only measure the number of links pointing to a site or page, but the importance of the site or page that provides the link.

The most well-known system for ranking sites based on link analysis is “PageRank”, which was developed by Google. As described by Google: PageRank relies on the uniquely democratic nature of the web by using its vast link structure as an indicator of an individual page’s value. In essence, Google interprets a link from page A to page B as a vote, by page A, for page B. But, Google looks at more than the sheer volume of votes, or links a page receives; it also analyzes the page that casts the vote. Votes cast by pages that are themselves “important” weigh more heavily and help to make other pages “important.”

Google’s toolbar (available here) includes an icon that shows a PageRank value from 0-10.

3. How do search engines work: PPC vs. SEO

It is important to know the difference between Pay-Per-Click (PPC) and Search Engine Optimization (SEO). PPC is a form of Internet advertising where advertisers only pay when a user actually clicks on their ad. With search engines, advertisers typically bid on keyword phrases relevant to their target market. When a user types a keyword matching an advertiser’s keyword list, the advertisements get displayed. Such advertisements are called sponsored ads, and they usually appear to the top and right of the “natural” or organic results on search engines (as depicted in the graphic below).


PPC advertising can be very expensive as target keywords cost in the upwards of a few dollars per click. This can really add up especially for keywords that receive thousands of clicks per day. Most small to medium sized companies hire SEO experts so they can boost their site’s “natural” or organic rankings, especially because their is no “per click” cost associated with organic rankings. Generally speaking, small to medium sized companies try to avoid PPC advertising, because it’s extremely expensive. This creates an even greater need for SEO services.

The most popular PPC advertising programs include: Google AdwordsYahoo Sponsored Search, and MSN adCenter. Other PPC programs include Ask Jeeves Sponsored Listings,ABCSearchMIVA, and SearchFeed. And this our explanation on How do search engines work?