@XxColdFangxX There are 23 different ranks in Rainbow Six Siege. Along with Operation Ember Rise, a new rank called Champions has been added to the game.
Every new season comes, Rainbow Six Siege ranking system works as follows;
Your old rank will be reset when a new season starts. If you play 10 ranked matches, your new rank will be determined.
When the new season starts, your MMR is recalculated by averaging your MMR from the previous season and 2500 MMR.
After the average is calculated, you will play 10 ranked matches and your new rank will be determined. From now on, you will earn or lose 100-120 MMR on average in every match you play.