All players start a standard poker tournament with the same amount of chips. As play goes on, the compulsory blinds and antes increase at regular intervals, and when a player loses all of their chips, they are out of the tournament.
The last player standing is declared the winner, and is rewarded with the biggest portion of the prize pool. The rest of the prize pool is distributed between a set number of players, depending on how many people entered the event.
You can find payout information listed in the tournament lobby of any Poker Stars tournament that has started running, along with the current status of the event. You can learn more by clicking the ‘Tournament Info’ button in the tournament lobby.