Search engines like Google need to find your site before they can crawl, index it, rate it, and display it in their listings (SERPs – or Search Engine Results Pages).
Google’s bots (the spiders Google uses) can access your page if they know your website exists.
Your site can only be listed in Google search if it is crawled and indexed by Googlebot in the first place. Google may not know about your site yet, however. There are several reasons why a site does not rank in Google.