Google Algorithm: How Are Search Results Ranked?

Google makes use of Page Rank, which is an algorithm to rank web pages and websites in search results. In the entire process, Google weighs the importance of websites to rank them accordingly. However, now question arises if Google makes use of the same algorithm to rank search results on 1^st page or does it uses different algorithms?
Source:[cualidosoft.wordpress.com]

How Social Media Sites Are Ranked?

You have heard about crawling and indexing and ranking. These three operations are of utmost importance to Google Webmaster Console. So, do you have any idea whether Social media sites like Facebook and Twitter are ranked in the traditional way or whether their signals are part of the ranking algorithm?[SOURCE:http://cualidosoft.wordpress.com/2014/02/07/how-social-media-sites-are-ranked/]