How it works at the table
The Independent Chip Model converts tournament chips into money. It exists because chips are not cash: doubling your stack does not double your prize expectation, since only one player takes first and everyone who outlasts a rival moves up the ladder for free. ICM prices every stack as a share of the remaining prize pool given all the stacks at the table, which is why the same all-in can be correct in a cash game and a disaster on a bubble.