Imagine you have a big box of toys that you and your friends like to play with. But you only have a certain number of toys in the box and you can't add any more. This is like a country's resources, which includes things like food, water, and money.
When a country sets a limit on the resources that it will use or allow in from other countries, this is called "national limited". This means that the country can only use or trade for a certain amount of resources.
For example, if a country sets a limit on the amount of imported goods it will allow from other countries, it means that there can only be a certain amount of those goods coming into the country. This is a way for the country to control how much they are using and trading with other countries.
Just like you and your friends need to share the toys in the box equally, countries also need to make sure that they are using their resources fairly and effectively. National limited is one way that countries can make sure their resources are being used properly.