Advancing timing - turning the pulley counter clockwise - you gain power at low RPM.
Retarding timing - turning the pulley clockwise - you gain power at high RPM
Most adjustable cam gears can be moved +/- 10 degrees which is 20 degrees of cam timing on most aftermarket cam gears.
Variable valve timing on the intake cam. 3 different setups. Seems to be popular on GT-R's in Japan now.
Parts for RB26 Timing Belt Change
Timing belt -13028-20P25
Tensioner Spring- 13072-58S10
Water Pump - 21010-21U26
N1 Water Pump - 21010-24U27