Is there a post which explains how the rankings are created?

You just start with a base rate 1200. Depending on if you win or lose, and the rating of who you win or lose to, a rating is calculated. A lot of the time there is an advanced mathmatical formula that dampens the rating shift the more games you play, that way there is not a giant fluctuation for fluke wins or losses.

Chess.com uses the Glicko system, designed as an improvement over the rating systems used by the USCF and FIDE. Google "Glicko" for more details.

here is a whole article on it: http://www.chess.com/article/view/chess-ratings---how-they-work

Wow. That was great. Thanks.