A lunchbox is like a special box that you use to carry your food when you go to school or work. It's just the right size for your food and maybe a drink too. Some lunchboxes even have different compartments inside to keep your food from touching each other or to keep things like fruits or veggies fresh.
You don't always have to use a lunchbox though. Some people might use a brown paper bag, which is basically just a big, folded piece of paper that you put your food in. But a lunchbox is better because it's sturdier and can protect your food better. Plus, you can use it over and over again instead of throwing it away like you would with a brown paper bag.
There are all kinds of lunchboxes, with different designs and colors. Some have pictures of your favorite characters or superheroes on them, and some might even have your name or initials on them. Whatever lunchbox you choose, it's important to always remember to wash it out so that your food stays fresh and yummy.