The concept of the game is very similar to the classic tamagotchis that were very popular towards the beginning of the century. That is, you have to feed your pet, play with him so he has fun, clean him so he is healthy, and ultimately give him the attention he needs.
As you do so, Pou will grow and, most importantly, the app will reward you with different things such as hats, clothing, or backgrounds for your small pet.. So, you always have incentives to keep taking care of him.
The best thing about Pou, however, is that he can communicate with other users of the app. That is, via the Internet you can visit your friends' Pous and receive other kinds of rewards.
Pou is an entertaining app that is experience lots of success for one reason: how incredibly addicting it is. You won't be able to stop taking care of your Pou once you start.