Search Engine Optimization SEO is a set of techniques and processes that search engines look for when their Automated Indexers visit your site.  SEO starts with submitting your site to major search engines which is called SES (Search Engine Submission).  After your site has been successfully submitted, the search engines Automated Indexers or Bots visit your site every few days.  They check your website for various items:

Content Relevancy Keyword and Keyword Phrases in your website’s content Meta Tag information in your website code SiteMaps formed in XML No database characters in dynamic URLS (?,=) Number of sites linking back to your site

In short, it can be said that the following equation is just one of many steps in getting visitors to your website