In-depth guide to how Google Search works
Guide from Google
Google Search is a fully-automated search engine that uses software known as web crawlers that explore the web regularly to find pages to add to our index. In fact, the vast majority of pages listed in our results aren’t manually submitted for inclusion, but are found and added automatically when our web crawlers explore the web. This document explains the stages of how Search works in the context of your website. Having this base knowledge can help you fix crawling issues, get your pages indexed, and learn how to optimize how your site appears in Google Search.