Closed manifold

A closed manifold is like a toy box that has a lid that fits perfectly on top. The box is a shape that doesn't have any holes or openings, and the lid covers everything completely. Just like how you can't see inside the toy box unless you open the lid, you can't see what's inside a closed manifold unless you look at it from every angle.

In math, we use closed manifolds to describe shapes that are completely enclosed and have no holes or gaps. Think of it like trying to draw a picture on a piece of paper without lifting your pencil or leaving any gaps. If you can draw the picture without any gaps, then it's a closed shape.

Closed manifolds can be really interesting and useful in math and science because they have some special properties that other shapes don't have. They can help us understand things like the curvature of space and how objects move through it. So just like how you can store all your toys neatly in a closed toy box, we can use closed manifolds to neatly describe shapes in math and science.