以下是关于In App Purchase的很好的解释

In-app purchase (IAP) means buying more content for the app through
Marketplace while in the app. Another name often used for them is
micro-transactions for the smaller purchases. Buying a new costume
for your character. You need several thousand gold coins to get that
pet cat in the game you are playing. You could play the game and
grind away killing monsters over several hours and earn the XP to get
the cat,or you could pay $2 now via in-app purchase and have the cat
straight away.

谢谢