Okay kiddo, so you know how some people live in different countries than you? And those countries might have different rules and ways of doing things? Well, sometimes those people owe money to someone in your country, but they don't want to pay it back. And since they're in a different country, it can be really hard for the person they owe money to, to make them pay up.
So, the rule against foreign revenue enforcement is basically a set of laws that says people can't just run away to another country to avoid paying their debts. It lets the person they owe money to go after them in that other country and make them pay up, just like they would if they were still in your country.
But, there are some exceptions to this rule. For example, if the person owes money for something that isn't allowed in the other country, they might not be able to go after them there. And sometimes, it's just too expensive or complicated to try to enforce the debt in another country. But in general, this rule helps make sure that people can't just ignore their debts by leaving the country.