A combo box is like a special container that lets you choose something from a list. It's kind of like a magic box that has a list of things inside, and you can pick one of them by clicking on it.
Imagine you have a box of crayons - you can only use one color at a time. But with a combo box, you can pick any color you want, without having to search through the whole box. The combo box has a special little arrow that you can click on, and when you do, it shows you a list of choices. You can then pick the one you want and use it right away.
For example, think of a website that asks you to pick your favorite fruit. Instead of having to type it in, you can just click on the combo box and see a list of fruits like apples, bananas, and oranges. You can then click on the one you like best and the website will remember your choice.
Combo boxes can be really helpful when you have a lot of choices and you want to make sure you're picking the right one. They're also used in things like computer programs and forms because they're easy to use and can save you time.