You can see more information about the coins and the coin game here:
Basically you get coins from bidding on and winning auctions. You also get coins from betting on the final price of an auction and being the closest guess. The highest coin holders will be awarded with prizes on a yearly basis. We launched the coin game in march, and will be announcing the first round of prizes in march 2018. We are looking for suggestions on how to improve the coin game and suggestions on what the prizes should be. So feel free to let us know what you think!