Google is the best ever search engine in the world. Have you ever think that why Google put some websites on the top and other on down pages. It all depends on Google search algorithm.
If you know how Google works on your website then you can also improve your website ranking.
Searching over the internet i actually found an info-graphic that is best and shows how Google Search Algorithm works.
Courtesy of: Quick Sprout
It clearly shows that create backlinks and adding more and more content to your website will give you best rankings. You must understand Google’s algorithm to rank your website on Google.