Actually, there's a bit more to it than that. You have to hit the wood in just such a way that it splits down pretty much the middle in order to get the right size pieces. Also you need to make sure the wood is of a proper age. Too old and it'll burn itself out before the fire gets good, which wastes time and effort as well as firewood. Too green and the wood will smoke like crazy, ruining the enjoyment of the fire and presenting a health risk that's far in excess of the benefits.
Well you can chop it whenever, but burning it is different. For burning, you want it to be dry. Not green or punky (rotten)
I love chopping firewood. I get to break something.
^^^