Cobordism

Okay, imagine you have two big puzzles. One is a puzzle of a round circle, and the other is a puzzle of a square. But, here's the catch: both puzzles have the same number of puzzle pieces, and all the pieces are the same size and shape.

Now, let's say you want to connect the two puzzles so they make one big puzzle. But, how can you do it? You can't just smoosh them together, because the shapes don't match up. What you need is something in between the two shapes that will make them fit together perfectly.

That's kind of like what cobordism is! Instead of puzzles, we're talking about shapes in the world of math. Specifically, we're talking about shapes that have the same number of "holes" in them. A hole is like a gap in the shape that goes all the way through it.

So imagine you have two shapes - one has one hole in it, and the other has two holes. They can't fit together perfectly, just like the circle and square puzzles. But if you add something in between them that has one hole, like a cylinder or a tube, then you can connect them! This "in-between" thing is the cobordism.

Basically, cobordism is a way of connecting different shapes in the world of math that have the same number of holes in them. And just like with the puzzles, you need something in between them to make it work!