How are the default search results are sorted on D7? I have a basic search configured on my site. I wanted to know how is the default search results are sorted in drupal, is it by the number of words found on the content or based on date the content is created or something else. I know it can be altered using custom modules. But I am curious to know how default on works.
Drupal's defaul search result is sorting on the basis of:


Number of comments
Keyword relevance
Content is sticky at top of lists
Content is promoted to the front page
Recently posted


Under Content Ranking configuration (admin/config/search/settings) you can setup the influence of the above factors while searching.

Thanks,
ARUN AK