This 2NT is an asking bid. It asks North whether or not he likes his preempt. If North likes his hand, he bids a new suit (or 3NT) to show a feature; an outside ace, king, or, ocassionally queen. The feature may not be shortness. 

South's hand for this is typically close to a notrump opener. South may have a five-card major as we tend to only bid a new suit after a preempt with a six-card suit of our own.