Organic Search: Organic search, also called natural search, is the process whereby a search engine determines results based on their relevance. Results yielded by this method, called organic search results, are often contrasted with ads that websites pay the search engine to display when users type in certain search queries.
Organic search is determined by algorithms taking into account a number of factors. Google and other search engines do not publish their exact algorithms in order to prevent exploitation through black-hat SEO techniques (techniques that boost a page’s ranking in the results through various tricks, rather than by providing real users with more relevant or high-quality content), but there is an entire industry dedicated to discovering and implementing these factors.
Organic search engine optimization, or SEO, refers to these efforts to make a website more attractive based on search algorithms. Organic SEO might include designing a website so that it can be easily “crawled” and indexed by search engines, editing content to include certain keywords at the proper densities, and marketing the site elsewhere to boost the number of backlinks—links to the site from other places on the web—it has.
There are also factors that negatively affect a page's ranking in organic search results. These penalties are applied, either manually by search engine employees or automatically, to websites in response to bad practices such as link farming.
SEO experts may also focus on a certain subset of results for which to optimize, such as local organic results.