The default value of 1 means that a single bounce is used to calculate how a surface's environment affects it. This is less accurate than a multi-bounce solution since in the real world photons bounce all over to illuminate the environment. However, the sacrifice in quality using fewer bounces is rewarded by increased performance versus more bounces. By increasing the number of indirect bounces, the indirect rays are fired from the initial surface and bounce off the first surface they hit, then continue traveling and hitting surfaces until the maximum number of bounces is met.