East opens 1NT 5332 shape is good to open with 12-14 HCPs.
South has a difficult decision, whether to overcall or not?
Not sure what has been taught, but it is important to compete against one of the best duplicate contracts of 1NT.
Here you have 9HCPs and a 5431 distribution that is on the left of the 1NT opener which increases the odds that the K♠ s is a trick. You may want to read this short article.
If you bid 2♥ s partner may be tempted to raise to 3♥ s, but it is an overcall of less than 15 HCPs otherwise he would have doubled so North should be cautious.
3♥ s may go off, but as you can see all Easts playing in 1NT made scoring +90 whilst one off in 3♥ s is only +50.
You may see with the little box that with best defence East should go off in 1NT. How?
South starts with the standard lead of 4♥ the fouth in longest suit that makes 5 tricks in ♥ suit. Many people will block the ♥ suit so only 4 tricks will be made at the start. North wins the first trick with the K over the Q. The normal play is to play the top of 2 remaining or the bottom with 3 remaining. So North will make the fourth trick with the 10♥ s.
Then North has to choose what to lead next. How?
You know the opposition has 12-14 + 8 HCPs = 20-22
Add your 10 and you now know partner has 8-10 HCPs.
You must not lead away from your K♦ .or K♣, so lead a ♠ .
This will give your side an additional trick with K♠, he can then cash the remaining 5th ♥ and North will finally make the K♦ ! One off.