See organic listings.  Organic Search is often referred to as SEO, search engine optimization, natural search or algorithmic search.  The act of performing an "organic search" involves completing a query using a search engine and looking at and eventually clicking on an organic (natural) result. 

Organic search consists of the unpaid listing of a search results page compared to the sponsored listings that are featured along the top on in the right side of a search engine results page.  The arrow in the screenshot below signifies the organic search results.