Okay kiddo, imagine you have a toy dinosaur and it's made up of many different pieces that fit together.
Now imagine there are different levels of detail that you can see in the dinosaur. Maybe you can see its overall shape, but if you look closer, you can see each individual piece that makes it up.
Progressive mesh is kind of like that! It's a way to show things on a computer that have different levels of detail.
When you look at something like a video game character or a 3D model of an object, your computer has to figure out how to display it on your screen. Usually, this means showing every single piece that makes up the object, one at a time. This can be slow and make it hard for your computer to keep up.
But with progressive mesh, the computer shows you the basic shape of the object first. Then, as you look closer or move around, it adds in more and more detail until you can see each individual piece. This way, your computer doesn't have to work as hard, and you can see things more smoothly.
So it's kind of like your toy dinosaur - you can see the overall shape, and then as you look closer, you can see each individual piece that makes it up. And that's what progressive mesh does for things on your computer!