Google cites three “key processes” in delivering search results.  Anytime an SEO effort is underway it’s important to ensure that these three areas are properly addressed.

1. Crawling
Crawling is how pages, either new or updated, are recognized, discovered, and “read” by Google.  Google uses a program called Googlebot that determines the pattern of searching sites, including where, when, and how much searching happens.  Google offers this as a free service and doesn’t accept payment to crawl a site more frequently.

2. Indexing
Once Google has crawled a site, it processes the site’s content and identifies words and positions of the words in the page.  All of this information is compiled in an index.  Google notes that this process has some limitations, including dynamic content and rich media content.

3. Serving Results
When a user enters a search term on Google, the returned results are what Google believes are the most relevant to the user.  Google determines relevancy by over 200 factors, including PageRank (the measure of importance of the page based on other pages linking to it).  Google continues to improve the discernment of quality links versus spam links.  Google also notes that content that is relevant and useful to the reader plays a big part in page selections and results.

Search engine optimization obviously extends far beyond these three areas, but these basic categories are important aspects of being recognized in the Google search process.

[Background information provided by Google Webmasters/Site owners Help]