Okay kiddo, an antiautomorphism is like a mirror image of a special kind of math thing called an automorphism. It's like when you look in a mirror and everything in the mirror is the opposite of what you're doing. That's what an antiautomorphism does to math stuff, it makes it opposite or backward.
Let's say you have a number like 5, and someone asks you to double it. So you do 5 times 2 and get 10. That's an example of an automorphism, because you're doing something to the number, but it's still the same kind of thing (a number) in the end.
But with an antiautomorphism, you'd do the opposite of that. So if someone asks you to double the number 5 with an antiautomorphism, instead of doing 5 times 2, you'd do something like flip the number around and get 52. It's still a number, but it's different now.
Antiautomorphisms can be useful in math because they help us see things from different angles, like looking in a mirror to see the back of your head. They may seem a bit confusing at first, but with practice, you can use them to solve all sorts of cool math problems.