Google Search is the web search engine of Google. The organic results are the unpaid results, as opposed to the ads that appear on the same page. Google states that it does not charge anyone to be in its index and does not accept payment for a higher ranking.
Google describes three stages. In crawling, automated programs called crawlers (Google's is Googlebot) download the text, images and videos of pages that they find through links or through a sitemap, a list of pages that a site owner submits. In indexing, Google analyzes each page and stores the information in the Google index, a large database. In serving, Google searches the index for pages that match a query and orders them by relevance, which depends on hundreds of factors, such as the user's location, language and device. Not every page passes all three stages.
Ads are the only thing Google sells in Search, so a listing in the organic results is free. Google Search Central publishes documentation for site owners about SEO (search engine optimization), the work of making pages easy to find and rank.