Okay kiddo, so first let's understand what "containment" means. It's like when you are playing with your toys and you want to keep them all in one place so they don't spread out all over the room, right? Well, in the big world, countries can also use "containment" as a strategy to keep another country from becoming too powerful and causing trouble.
Now, when we talk about the "China containment policy," it means that the United States government and other countries are trying to keep China from becoming too powerful and possibly causing trouble for other countries.
See, China is a very big and important country with a lot of people and resources. In recent years, they have been growing very fast and becoming more and more powerful. But some people worry that China might use this power to do bad things like take over other countries or harm their own people.
So, to try and prevent this, the United States and other countries have been working to prevent China from growing even more powerful. They do this in various ways, like making alliances with other countries that might be threatened by China, trying to limit China's access to certain technologies or resources, and sometimes even putting economic sanctions on China.
The idea behind this policy is to try and balance out the power between countries so that no one country becomes too dominant and causes problems for everyone else.
Does that make sense, kiddo?