A natural edge bowl is a wooden bowl with the bark or live edge of the tree as the rim of the bowl. Instead of having a flat top, a natural edge bowl often has a high point and a low point due to the "round" of the tree trunk. Having the bark or live edge on the rim of the bowl adds so much character to the piece in my opinion. If the natural feature is there on your turning blank, why not use it! In most cases it maximizes the size of your bowl so your not wasting as much wood.