Okay kiddo, you know when you were born and you got a birth certificate with your name and the date you were born and all that info? Well, some people don't get that because they don't have a country that says they belong to it. This is called being stateless. It's like not having a home country or a family to belong to.
In 1961, some grown-up leaders from different countries got together and made a rule called the Convention on the Reduction of Statelessness. The rule said that every country should try really hard to make sure that no one is stateless.
So, countries have to try to give people a citizenship, which is like a ticket to belong to a country. It makes sure that they have a home country and protections that come with that. The convention also says that countries need to make sure that if they change their rules about who can be a citizen, they can't leave people who were already citizens stateless.
Basically, this rule is like making sure everyone has a home and someone to take care of them. It's trying to be fair to everyone and make sure nobody is left alone without a country.