Google will never tell you how the ranking algorithm works because if they did, the ranking algorithm would be gamed. Basically, the problem is a lot of people will try to get less relevant content to rank higher than the best content. If you tell these people how Google's ranker works, they will make Google search worse because they will learn how deceive the ranker.

A ranker is a piece of software which determines what results should be show to a user on the search results page.