This is a game where someone simply posts a drawing that they have drawn and the person that posts next rates it and so they post another picture that they drew and so on.
If you don't get it, here's an example:
Person 1: *posts drawing of donkey with sunglasses*
Person 2: 7/10
*posts drawing of Elvis*
Person 3: 10/10
*posts drawing of a pickle in a hat*
That's pretty much how it works.