It's played by over 130 million people a month.
It's Candy Crush Saga
It's available on Facebook, Apple and Android devices.
You match candies to score points and you need to achieve objectives before you can clear a level.
The game is free, but you only have five lives that take a half hour each to regenerate.
Part of the reason the game earns so much money is the option to purchase lives, as well as in-game power ups
Be forewarned, it's quite addicting. I'm stuck on level 361 right now and so far I've held out from spending any real money, but I've been close.