A
Cud affect the outside edge of the die. A piece actually breaks away from the die:

With this void, when the die strikes a new coin that area of the coin will be unformed/taller than the other devices:

On this you can see the chipping away more of the die as it is continued to be used. It progressively gets worse.
On the opposite side you can see the weakness because the lack of metal opposite that area.

On a die chip the area in the central areas it is just part of the die that breaks away. The opposite side of the coin is not affected. The rim is not affected, thus it is not a
Cud. (some sites may call them this, but that is not the accepted term by all collectors)