How Search Engines Work
To understand what SEO is, you need to understand how search engines work.
Everyone knows what a search engine is - you use it to search and find information from the world wide web. Examples include Google, Yahoo, and Bing.
Search Engines have 4 main functions:
3) Calculating Relevancy & Rank
4) Serving Results.
Let’s go over each of these functions and how they relate to each other.
Search Engines use automated robots to crawl web pages for content. These robots are known as crawlers or spiders. They crawl the entire world wide web.
To better understand how this works, we're going to use helpful analogy from SEOMoz which compares the world wide web to a subway system.
The subway system has large network of stops all over the city.
The stops represent documents such as web pages, images, or files on the Internet, while the subway tracks between stops represent links.
So crawlers will “crawl” the entire subway network by going through each path to find all the various stops. This is how they find all the data that exists on in the world wide web.
Building an Index
Once the crawlers find these pages, they take the code and store parts of the pages in large databases.
These are the databases that search engines reference when they provide you with search results.
Calculating Relevancy and Ranking
To provide accurate information and build accurate databases, search engines must evaluate two important things about every piece of content:
Relevancy - how relevant the content is to your original query.
Ranking - how valuable and important is this content?
Search engines use secret algorithms to determine relevancy and ranking. Items that have high relevancy and high ranking show up first in search results.
As a result, Search Engine Optimization focuses on improving the relevancy and ranking of web sites, so that content will show up earlier in search results.
There are countless factors which influence relevancy, which mean it’s not just about stuffing a bunch of keywords on your page anymore. We’ll talk more in depth about how to have higher relevancy when we offer SEO tips. Right now it’s important to just understand what relevancy is.
Likewise, a number of factors influence ranking, but one of the most important is popularity. How popular is a particular piece of content? The more popular it is, the higher the ranking.
After you enter a query, search engines will look at their databases and retrieve the best results, as determined by them. This is usually in the form of an organized list of search results, with the most important results ranked first.
So now you know how a search engine works. Next time we’ll go into more depth about some best practices for actually using this information to improve your site’s rank.