lol thats alrite im glad u asked, topping is basically a technique used to make a plant shorter and bushier than it would have been before, it also increases yeild, which is always a good thing. now i will try to explain how it does it...

[attachment=o97635]

When you normally grow a cannabis plant there is one main stem, (C. in above pic) which houses the main cola (A. in above pic) the main cola is like the brain for the plant, and basically tells the rest of the plant how to grow, by removing this, everything runs on its own clock, and grows as it wants, when you cut the top off the plant cannot continue growing the main stem, instead the growth on the nodes (B. in above pic) receives all the plants energy and begin to grow at a much higher rate, the reason you want these branches to grow more is because these are the branches that produce buds, some say removing the main cola is a stupid idea, and that it has the 'best smoke on the whole plant' - this is not true, the main cola is more dense, but not necesserily (-excuse the spelling) any more potent, topping is just another method used to get a bigger yeild, and i can see why, another thing you might want to find out about is LST i think its something like low stress training but im not sure... anyway hope that helps...