http://ex_knife.tripod.com/excalibursknifeezine/id11.html
- The Belly
The belly of a blade is the curving section under the point. Some knives do not have a curving section (Americanized tanto), while on other knives, most of the entire blade is curved. (skinner) The belly increases the knife's ability to both slice and slash. It presents an ever-changing angle to the material being cut, and this means slicing efficiency is preserved across the cut.
If slicing and slashing are important to you, you want to look for a nice curving belly. However, there are always tradeoffs. Typically, the more belly a knife has, the less acute its point. So you get better slicing, but piercing ability goes down. Trailing point skinners are basically all belly, because they were designed to perform tasks such as skinning big game. On the other hand, a dagger has no "belly". The dagger knife has an incredible point for piercing but is not a great slicer/slasher.
So you trade off belly (slicing) for point (piercing). But there are some compromises. For example, if the knife design has lots of belly for slicing, the designer can clip the point and add a falsed edge top to make it a bit sharper.