Three scenarios

Dealer South, E/W vul. Herer’s your hand as West:

South opens 1NT and North-South quickly reach 3 No-Trumps:

What do you learn from the auction?
North’s Stayman reveals that he has four Hearts and given that he shows strength in Clubs and then passes 3NT, you understand that he is afraid of Diamonds (probably he has shortness there). South has four Spades and must have solid Diamond stoppers; after all, he bid 3NT over 3♣ knowingly.