During the course of cent production, obverse and reverse dies may develop a break defined by an area from the edge of the coin and some area associated with the face of the die.  These breaks occur as a result of a portion of the die becoming separated from the die has a whole.  These breaks are usually seen as raised areas on the coin surface where a void has formed on the die due to the loss of that portion of die.  Since the die has a void in this area, it will be raised on the resulting minted coin because of metal flowing into the die and filling the void formed from the break.  Certain die states will show these cuds with full detail because the separated piece of the die is still retained.  

In order to be listed within this index, a die break must adhere to the above conditions and contain both rim and at least some portion of the die face.  Dies that have breaks that do not satisfy the aforementioned area of the break are merely die breaks or rims breaks.