Hello kiddo! Do you know what it means when someone says "opt-out"? It means that someone wants to choose not to do something or give permission for something. Kind of like when you decide not to have dessert after dinner because you want to be healthy.
Now, let's imagine you are playing a game with your friends and one of your friends wants to "opt-out" of playing. They are saying "no thank you, I don't want to play anymore". That's what it means to opt-out.
In the grown-up world, there are other ways to opt-out. For instance, you might receive an email asking you to sign up for a cool new service, but if you don't want to sign up, you can "opt-out" by clicking on the link in the email that says "unsubscribe". This tells the company you don't want to receive any more emails from them.
So, to summarize, opt-out means to choose not to do or give permission for something. It's kind of like saying "no thank you".