Organic search results are listings on
search engine results pages that appear because of their relevance to the search terms, as opposed to their being advertisements. In contrast, non-organic search results may include
pay per click advertising.
The
Google,
Yahoo!, and
Bing search engines combine advertising and search results on their search results pages. In each case, the ads are designed to look similar to the search results, though differ in formatting enough for readers to make distinctions between organic results and ads, such as their background colour and/or placement on the page. Further, the appearance of the ads on all major search engines is so similar to the genuine search results that a large majority of search engine users cannot effectively distinguish between them.
[1] Since this study is 9 years old, it is likely that many more search engine users are able to distinguish between organic search results and advertising.