SEO is the process of optimizing your website for the purpose of getting free (organic) traffic from search engines to your site. An optimized website is more easily understood by search engine crawlers and this increases the chances of ranking higher in SERPS (search engine result pages).
Crawling the web
Search engines run automated programs, called “robots” or “spiders”, that use the hyperlink structure of the web to “crawl” the pages and documents that make up the World Wide Web.
Once a page has been crawled, its contents can be “indexed” – stored in a giant database of documents that makes up a search engine’s “index”.
When a request for information comes into the search engine, the engine retrieves from its index all the document that match the query.
Once the search engine has determined which results are a match for the query, the engine’s algorithm (a mathematical equation commonly used for sorting) runs calculations on each of the results to determine which is most relevant to the given query.
Paid & Organic results
Paid search provides immediate top-of-the-page listings and greater click-through rates, i.e., sales when consumers are ready to purchase.
Organic ranking gives a business credibility and evergreen search results.