How to Read Search Engine Results Pages
Check out the big two: organic and Pay Per Click.
Search results are mostly dominated by two particular indexes: the organic or natural search results, and the PPC (Pay Per Click) search results.
The organic-results index is created by searchbots. For instance, Google uses something called a googlebot to retrieve pages. It’s common to talk about searchbots as if somehow they wander around the Web, moving from page to page through links between the pages, collecting the pages, and sending them back to home base to be analyzed and indexed.
The search results typically put ten results from the organic index into the search-results page, though, those results are often interspersed with other types of search results. (In some cases, in particular when adding local results to the page, the search engines may display a smaller number of organic-search results, perhaps seven or eight.)
Today, the three major search engines all display PPC ads, ads that cost the advertiser nothing until someone clicks the ad, at which point the advertiser is charged instantly.
PPC ads are typically placed at the top of the search results (three or four results, though sometimes Google omits the top ads) and in a column to the right of the main search results.