Look, ranks are based on the experience you gain in any match, from premier mode to arms race. They are essentially comparable to ranks in the army, from recruit to marshal. VRedux described this very clearly in the CS2 rank system overview, which you can read at your leisure. By the way, when you reach level 50, you will receive a medal for service, which will be visible to all players and will be your distinguishing mark. Since I have been playing CS 2 for a long time, I already have 4 such medals for each year of play, plus several additional marks for premier mode. It took me a very long time to achieve a rating of 20,000, and I hope to maintain it at the same level.