From what I understand, it's an International rating. They use the same in other countries. How they get it...I have no idea. 1600 rating is a fairly good rating. It means that you are a strong player. 1800 is considered advanced as you may know and is very difficult to obtain.
Hope I helped
~Thankyou(1123)
When you play the chess.com computer outside of live chess what is the estimated rating (ex. medium~1600) relative to? Is that the chess.com rating system, elo, or some other type of rating?