Why can i still play my game on my ipad eventhough i only downloaded few kb's of the app?

Why can i still play my game on my ipad eventhough i only downloaded few kb's of the app?

I downlaod the app on my pc via itunes, and the i plug my ipad into the charger, then it auto-sync.

But then i noticed that the game icon appears on my screen. So i clicked it and end up playing it for few hours, eventhough i only downloaded few kb's of the game. I'm still in my confusion. Does it have anything to do with the icloud?