When a user searches for a keyword or phrase, search engines provide them with a list of results that are ranked by their relevancy and authority. These lists are called Search Engine Results Pages (SERPs).
For example, if you were to search for "widgets" on Google, the list of sites, articles, blogs, studies, images, and other results that you'd receive is the SERP.
SERPs contain two types of results: organic and paid. The organic SERP listings are the "natural" listings -- the ones that the search engine's algorithm found to be the most relevant to the searched term. The paid SERP listings are the "sponsored links" -- the ads usually displayed above and to the side of the organic listings.
The vast majority of search engine users only rely on the organic listings. In fact, 70% of the links that search users click on are organic, while as much as 80% of search users ignore the paid listings.
Of these organic listings, the top 10 are the ones that receive the most attention. A recent study reported by Search Engine Watch found that the top listed organic result on Google's SERPs overwhelmingly receives the most traffic. According to the study, 33% of search users go to the top ranked organic listing. The second ranked organic listing only receives about 18%, third receives about 11%, with fourth through tenth receiving a nominal amount of traffic. Results number eleven and up receive virtually no traffic, which is no surprise considering the fact that three quarters (75%) of search users never look past the first SERP.