Okay kiddo, have you ever played a game with your friends where you all have some toys and you want to make sure that no one is cheating or being mean to anyone else? That's kind of what the "Autorité de la Concurrence" does, except with companies instead of toys.
You know how there are big stores like Walmart or Target, and smaller stores like the ones you go to with your parents? Well, the Autorité de la Concurrence makes sure that all these stores play fair with each other, and don't try to be mean to each other just to make more money.
For example, imagine if Walmart tried to make it really hard for the smaller stores to sell things by giving them bad prices or not letting them have access to certain things they needed. That wouldn't be very nice, would it? And it wouldn't be fair either.
That's why the Autorité de la Concurrence is there. They make sure that everyone who wants to sell things can do it on an equal playing field, so that no one gets an unfair advantage over anyone else. They also make sure that companies act nice to each other, and don't try to bully or force each other into doing things they don't want to do.
So, in short, the Autorité de la Concurrence is like the referee in a game of toys, making sure that everyone plays by the rules and treats each other nicely.