How Google Search Engine works in SEO|Crawling Indexing in SEO|Search Engine Algorithms:-
Google is a very popular search engine which is used to search textual, audio and visual content in the internet world. Beside google there are other search engines like bing,AOL,Ask.com, Baidu and Duck duck go etc.Google uses a special algorithm to generate search results. While Google shares general facts about its algorithm, the specifics are a company secret. This helps Google remain competitive with other search engines on the Web and reduces the chance of someone finding out how to abuse the system.
Every Search Engine work in the same manner, like Google. Google search engine first crawl and index whole web site word by word and then google algorithms examine that every content according to search engine optimization rule, if that content according to rule then google search engine rank that content, otherwise no.
Below is a video tutorial from which you can understand how Google search engine works.