Here is a die that has a crack on the die.

See red arrows.

Here is a die that would be striking a
Cud on the coin from this point on.


A
Cud happens because a die of the die has broken away from the die. This void will leave the coins struck after this happens with an area not formed. Also because this part of the die is missing the coins will be weak on the opposite side.

(note the weakness on the reverse)
When the die splits off, you have two pieces:

Some may call die chips a
Cud. That is not correct. Nothing on a chip breaks off the side of the die. Chips are pieces of the dies face that have broken/chipped away from the die.
