From the Arena site:

Now you can chose yourself! Play for FREE or play for CASH in today’s big update of the SK Gaming Arena platform. Win CASH or HARDWARE prizes, the choice is all yours. All in our brand new challenge and ladder features released today, that will bring you more fun, more games and even better prizes to win.

What are the Monthly Challenge Ladders?

- PLAY FOR CASH LADDER: The monthly CASH challenge ladder displays the players with the most played challenges this month. There’s a monthly prize pot of €1000 to be distributed among the Top 50 players in the ladder, which will be released when a minimum of 500 CASH challenges have been played within the given month by all the site players. Want to be one of the winners? Then get some challenges going and play some games!

- PLAY FOR FREE LADDER: The monthly FREE challenge ladder displays the players with the most challenge wins the current month. There’s monthly hardware prizes to the TOP 3 players on the ladder, which will be released when a minimum of 500 FREE challenges have been played within the given month by all the site players.

You can view both Challenge Leaderboards on the overview page for the Leaderboards, to see what your ranking is and how many more challenges you need too make, too secure yourself one of the great CASH or HARDWARE prizes in the given Leaderboard.

With that update we have also updated the player profiles to now display both CASh and FREE statistics, so your challenge stats don't get all mixed up.