Google is the world's most popular search engine, and intends to stay that way. Its popularity is a reflection of its aim to provide the best possible user experience.
Today, that means a secure experience, which is why Google now boosts a site's SEO (Search Engine Optimization) ranking if it secures the entire user session by HTTPS. Essential to a site's success, SEO helps a business to be found, so higher ranking means more site traffic.
Google's ranking algorithm is constantly evolving and is highly confidential. But it is known that Google's spiders crawl websites and currently rank based on key criteria.