INTOSAI stands for the International Organization of Supreme Audit Institutions. It is a group of people from different countries who work together to make sure that a country's money is being spent properly. Much like how your mommy and daddy manage your piggy bank to make sure you spend your money wisely.
In the case of INTOSAI, they work with different government auditing offices to check if their money is being spent in a way that is fair and helps their country in the best possible way. They also help these governments create good financial policies and procedures to make sure their money is being spent in ways that prioritize the people's needs.
So basically, INTOSAI is like your mommy and daddy checking your piggy bank to make sure you're spending your money in a smart way to help you grow up to be smart and responsible with your money.