ELI5: Explain Like I'm 5

3-manifold

Okay kiddo, let's start with imagining a piece of paper. Now fold it in half. What do you see? You see two sides or regions, right? Now imagine if you fold it again, you will get four regions. Great! Now imagine if you fold it one more time, you will get eight regions. Isn't that cool? We call this kind of folding a crease pattern.

Now, let's imagine something called a 3-manifold. It's a three-dimensional space that can be divided up into smaller parts or regions, just like how the paper can be folded into smaller regions. But here's the catch, these regions or parts are a little different from the paper. They are not flat, and you can't really fold them like paper to get different shapes.

A 3-manifold is kind of like a puzzle made up of many different pieces, and each piece can be twisted and turned, just like how you move a puzzle piece to fit it in the right spot. When you put all the pieces together, you get a three-dimensional shape or space that looks like a creature or an object in real life.

For example, think of a ball. A ball is a perfect example of a 3-manifold. If you take a closer look, you'll see that a ball is made up of many smaller parts or regions, just like a puzzle. If you try to flatten out any of those regions, you'll see that they don't look like a flat piece of paper. They have a curved shape that connects to other regions in some way. That's what makes a 3-manifold so special – its parts are curved, but they fit together perfectly to make a whole.

So, to sum it up, a 3-manifold is a three-dimensional space that can be divided up into smaller parts or regions. These regions are not flat like a piece of paper, but they fit together in such a way that they form a shape similar to an object or creature in real life. Think of it like a puzzle made of many different pieces, each of which can be twisted and turned to create the final picture.