Okay kiddo, so let's say you really want a toy gun but your mommy won't let you have one. So, you ask your big brother to buy it for you instead. That's kind of like a straw purchase.
A straw purchase is when someone buys something, like a gun or a car, for someone else who can't or shouldn't buy it themselves. Sometimes people do this for good reasons, like if they're buying a car for their elderly parents who can't physically go to the dealership. But other times, people do it for bad reasons, like if they're buying a gun for someone who shouldn't have one, like a criminal or someone who's not allowed to have a gun.
It's important to remember that straw purchases are illegal and can get you in big trouble. So if you ever want something but can't buy it yourself, it's always better to ask mom or dad to help you out instead of asking someone else to do it for you.