De Finetti's game is a game that uses probability to test how well you can guess things. It's like a game of chance. You will be given different possible outcomes and asked to guess what will happen. You can think about all the different possibilities in the game and determine how likely which outcome is more likely. You will get points for correct guesses, and lose points for wrong guesses. The goal of the game is to get the most points by the end of the game.