Search engines, such as Google, are highly complex implementations of software technology that have evolved into mega-businesses, and certainly Google is a colossus when it comes to providing access to the information you can find on the Internet.
Note: Google is far and away the most important search engine. So SEO experts tend to focus on Google. But most other search engines work basically the same way that Google does. By better understanding Google's mechanisms, you'll also be able to improve your placement with other search engines.
Effective SEO requires a basic understanding of how the pieces of search engine technology fit together.
A search engine, such as Google, implements four basic mechanisms:
Discovery, Storage, Ranking, and Return (DSRR) are all important to SEO. In particular, you'll need to have a basic grasp of Discovery and Ranking in order to be effective with SEO implementationso these mechanisms are explained in greater detail later in this article (see "Using PageRank").