Unlike most games nowadays, Coins form the only currency in Subway Surfers. That means that, refreshingly, there is no premium currency where the game keeps asking you for money. Instead, everything in the game can be purchased using the Coins that you collect on each run. While some items may be prohibitively expensive, effectively forcing you to use real money to buy them, this is far preferable to having a fenced-off premium currency like most free games do.
Coins can be used to purchase items in the Shop
Using Coins you are able to purchase upgrades, power-ups and new characters. Also, you can skip any missions that you are finding too troublesome by shelling out some of your hard-collected coinage.