ANSI ASC X9 is a group of grown-up (like mommy and daddy) rules for how banks and other people who deal with money should keep it safe. Just like how you keep your favorite toy safe in your toy box, the banks and companies keep money very safe too.
ANSI stands for "American National Standards Institute" which is a big group of people who make sure important things like how to keep money safe have rules. ASC stands for "Accredited Standards Committee" which are the specific people who work on these rules for the banks and companies. And X9 is just a fancy name that they came up with for this group.
These rules make sure things like the special passwords we put on our phone to keep it safe, are being used by the banks too. They also make sure that the people who work at the banks are trained to keep our money safe and not tell anyone else. They helped create special ways for when you swipe your debit or credit card, your money stays safe and not stolen by bad guys.
Overall, ANSI ASC X9 is a group of people who make sure that banks and companies follow some important rules to keep our money safe just like how mommy and daddy keep their important items safe.