Okay kiddo, so there are some states in the US that have special rules about how you can buy and sell alcohol. These states are called "alcoholic beverage control" (ABC) states.
Basically, they have a special agency called the Alcoholic Beverage Control Board or Commission that controls everything related to alcohol. They make the rules about who can sell alcohol, how much they can sell, and who can buy it.
In these states, you can't just walk into any store and buy alcohol like you might buy candy or toys. You have to go to a special store that's owned by the state or the government. These stores are called "ABC stores." They are the only places where you can buy alcohol.
The government thinks this is important because they want to make sure that people who are too young or too drunk don't get their hands on alcohol. They also want to make sure that the businesses who sell alcohol are following the rules and not doing anything illegal.
So that's what an ABC state is all about - it's a state that has special rules about buying and selling alcohol, and a special agency to make sure those rules are being followed.