Capital control is like a grown-up's way of saying "You can't bring all of your money to the candy store".
Imagine you have a big piggy bank and you want to go to the store to buy some candy. Usually, you could take all of your money out and bring it with you. But sometimes, the grown-ups in charge say that you can only bring some of your money with you. They might do this because they want to make sure you don't spend all of your money on candy and have nothing left for things you really need, like food, clothes or books.
In the same way, capital control is when a government or a bank puts some rules in place to limit how much money people can take out of their own country or move around in different ways. This is done for a variety of reasons, like controlling inflation, stabilizing the value of the money, or protecting important industries.
So, in short, capital controls are like grown-up rules to make sure people don't spend all their money on candy and have enough left for other important things.