It means Independent Chip Model. This is a method of calculating your winnings based on the proportion of chips of each player when you are awarded prize money (ITM). Indeed, this principle is based on the fact that the chance that a player has to win the game is proportional to his amount of chips at a given time. It takes into account several variables and allows you to determine the risk/reward ratio during one hand. It generally consists of converting the amount of your stack into real money based on the payment structure (payouts).