The Customs Convention on Containers is like a set of rules agreed upon by different countries to make it easier to transport things in big metal boxes called containers.
Imagine you have a lot of toys to bring to your friend's house for a playdate. If you tried to bring them all in your arms, you might drop some or get tired carrying them. But if you put them all in a big box with handles, you can easily carry the box and keep all the toys together.
That's kind of like what containers are for shipping things from one country to another. But each country has different rules about how things can be transported and what kind of containers can be used.
The Customs Convention on Containers helps make things easier by creating standard rules and regulations for containers used in international trade. This means that the countries can agree on things like the size and weight of containers, how they should be labeled, and how they should be inspected for security reasons.
So, just like how your parents might have rules for how you and your toys should behave while visiting your friend's house, countries have rules for how containers should behave while traveling from one country to another. And the Customs Convention helps keep everyone on the same page so that things can go smoothly and efficiently.