The geometry tells you about how the blade was made. A good geometric shape for a blade is flat but slightly rounded: the two faces of the knife should bulge outwards, providing more material above the edge and allowing this part of the blade to be sharpened thinnly. The convex form also pushes the material being cut apart and keeps it from cleaving to the blade. Some knives have slightly uneven faces: this allows small pockets of air to form between the blade and foodstuffs being cut, helping them to slide off the face.