A restricted product is something that you are not allowed to buy or use unless you are old enough or have permission from someone in charge. It's like trying to buy candy before dinner – your parents might tell you that you can't have it until after you finish your meal.
For example, some medicines are restricted products because they can only be taken by adults or people with a doctor's prescription. Guns are also restricted products because they can be dangerous and require a special license to use. Other restricted products might include cigarettes, alcohol, and lotto tickets – things that have laws or rules about who can buy or use them.
So basically, restricted products are things that are limited or controlled to keep people safe and healthy. Always make sure to ask an adult or someone in charge if it's okay to use or buy something that you're not sure about.