CryptoKitties is a digital goods trading game that lives on the Ethereum blockchain. It lets you purchase, trade, and breed digital kittens. The game has no straightforward "goal" — you can simply buy a digital kitten, and it will eternally be yours due to the nature of blockchain technology.
However, kittens come with different visual features, called traits, and some of these traits are rarer than others. Naturally, most users are trying to breed rare cats, not only because they look cool, but also because they can be very expensive; one particularly rare cat was recently sold for more than a hundred thousand dollars.
In fact, the total kitten sales so far are around $3 million dollars; pretty impressive given the game launched last week.
Article: http://mashable.com/2017/12/04/how-to-play-cryptokitties