Have you ever played with a ball or a balloon? When you look at them, they are round all the way around and you can squeeze them from any direction and they still stay round. That's because they are convex shapes! A convex shape is a solid object that is round and smooth and doesn't have any dents or curves on its surface.
Another way to think of a convex body is like a bubble. When you blow a bubble, it's round and smooth all the way around, right? That's because it is a convex shape too!
Convex shapes are very important in lots of things like math, science, and engineering. They help people design buildings, cars, and even space shuttles! So next time you see a round and smooth object, you'll know that it's a convex body!