When you buy something, like a toy or a TV, sometimes you might change your mind later and decide you don't want it anymore. That's okay! The cooling-off period is a time when you can change your mind and return the thing you bought to the store.
Think of it like taking a break after a game of tag. You got all hot and sweaty running around, so you need to cool off before playing again. The cooling-off period is like that break, giving you some time to cool off and think about if you really want to keep the toy or TV you bought.
The amount of time you have for the cooling-off period might be different depending on where you live and what you bought. Sometimes it's a few days, and sometimes it's longer. During that time, you can take the toy or TV back to the store and get your money back.
But there are some things you should know. You can only return the toy or TV if it's still in good condition - no scratches or broken parts. You also usually have to have the receipt to prove you bought it in the first place. And some things, like food or custom-made things, can't be returned during the cooling-off period.
So, the cooling-off period is a time when you can change your mind and return the things you bought to the store, but only if it's in good condition and you have the receipt.