Topping is the removal of a single flowering site to create multiple. You can top any branch on a cannabis plant by cutting it and exposing flowering sites lower in the canopy. When these lower flower sites are exposed, they will grow rapidly and eventually become the new main branches within the plants’ structure.
Topping should really be limited to the vegetative stage of growth. Topping is a great way to increase yields and even out a canopy. Like anything in life, over-topping isn’t a good thing and can reduce yields in certain genetics.