No offense, but you should read a little before you ask questions. Since we are such nice people I will go ahead and answer though. First let me describe something.

Picture the plant as having a stem with sets of leaves connected to that stem via another stem. Lets say they are connected to each other at a 90 degree angle. In between the main stem and the leaf stem grows what is considered to be a clone. They call it a clone because it is a whole seperate plant growing on that plant. It grows to have its own leaves and its own clones. Topping is cutting the top of the plant so that the nearest clones to where you cut will start to grow a lot faster. This happens because the plant responds and decides these are the next best place to put its energy into. This in turn creates two tops. Obviously you can do this more than once and turn two into four. However, everytime you top a plant it goes under stress and sometimes stunts in growth (pauses). So it has its good sides and its bad sides. Goodluck.