The League system in Palace of Cards currently consists of four categories. It determines the following:
The best player of the day by number of points earned
The monthly winner by number of Chips earned
The champion of the quarter by number of points earned
And the rating according to TrueSkill
Further information can be found on the relevant info page.
Good to know: Leveling is not part of the League! Hence, if you would like to know more about levels and experience points, please click here.