How the Ranking system works?

I can understand the basics of how you’re placed in divisions but it would be cool if somebody who knew could explain how it works.

For example how do you get from Onyx to champion, what the number 1500 means and so on?

Onyx is the top bracket of players, 1500 is your raw CSR score.

The top number (200?) Onyx players are placed in Champion and given a numerical placement. There’s a blog post floating around that explains it somewhere.