You can earn rewards like attacking other player villages, and shields to protect your village. There is a slot machine, you have to spin it and boom you’ll get different rewards from it. This game is so simple that anyone can play it. You have to build a village with the help of a slot machine. But if you want to know what exactly is coin master then, Coin master is a game where you can build your own castle.
If you ever played the game then, I think I don’t need to tell you anything.