Hi there buddy! So, the individual mandate is a rule that says everyone in a country has to have health insurance. It's kind of like when you have to wear a helmet when you ride a bike, because it's the law and it keeps you safe.
The reason why the government has this rule is because when everyone has health insurance, it helps to keep the cost of healthcare down. That means people will be able to go to the doctor when they're sick without having to worry about how much it will cost.
So, if you don't have health insurance and you don't have a good reason for not having it, like if you're too young or too poor, then you might have to pay a fine for not following the rule.
The individual mandate is just one part of a big law called the Affordable Care Act, which was designed to help more people in the United States have access to healthcare. Does that make sense, little buddy?