3NT, 4♥, 4♠, 5♣ and 5♦ are called 'game' contracts. Any contract below game is called a 'part-score'.
Competitive bidding and the part-score battle
8 cards in the same suit between your hand and partner's is called a 'fit'.
If you can find a fit in any suit then tell partner the good news by supporting that suit even if it means bidding to the 2 or 3 level.
South has a heart fit and bids 3♥
Constructive bidding and the game bonus
You win extra points for bidding and making a game. If you and your partner have 25+ points between your two hands then go for it!
North showed 12-14 points, South has 13. That's 25!