Texas hold 'em
As players bust out of the tournament, the average player's chip stack gets larger. In order to insure that the blinds do not become insignificant in the face of the growth in chip stacks, tournaments are played in timed "rounds." At the beginning of each round typically the blinds increase. Every few rounds there will be a short break between rounds. For tournaments that last longer than a day, there will be a last level for the day, and the tournament will resume the next day.