what is the difference between a 2 pole, 4pole or whatever pole?

[zeropointbug]

That's interesting, I am not familiar with the way it terms a few things though, for instance # of poles. In the industry, when someone refers to a motor having 4 poles, I have always known it being 4 poles per phase, times the # of phases you are driving.

It also says a brushless DC motor has square back EMF waves, how can that be? It's a natural movement and a natural wave would follow.