So the qualifier "organic" was invented to distinguish non-ad search results from ads.
[4] Because the distinction is important (and because the word "organic" has many metaphorical uses) the term is now in widespread use within the search engine optimization and web marketing industry.
Google claims their users click (organic) search results more often than ads, essentially rebutting the research cited above.
[6] The same report and others going back to 1997 by Pew show that users avoid clicking "results" they know to be ads.
[7][8] Organic SEO describes the use of certain strategies or tools to elevate a website's content in the "free" search results.