ELI5: Explain Like I'm 5

Stone duality

Stone duality is a way of describing two different types of things called Boolean algebras and stone spaces. It's like saying there are two different kinds of toys: Lego and dolls. They're both toys, but they're not the same kind of toy.

A Boolean algebra is like a toy set that has rules for how you can combine different pieces together. For example, imagine a set of blocks that can either be red or blue. You could combine two red blocks to get another red block, but if you combine a red and a blue block, you get a different kind of block altogether (purple). Boolean algebra is a set of rules like this that tells you what happens when you combine different pieces in different ways.

On the other hand, a stone space is like a special kind of toy house that you can build out of blocks. Imagine building a house out of Legos. Each Lego block has a special shape that can fit together with other blocks to make interesting shapes like walls and roofs. A stone space is like a special kind of Lego house that you can build from blocks that have special shapes and properties. These blocks represent different "points" in the space and the way they fit together lets you describe the shape of the space.

So stone duality is just a way of saying that there are two different ways to think about these two types of toys: as a set of rules for combining blocks (Boolean algebra) and as a way of building interesting shapes out of blocks (stone space). It's like saying you can play with Legos either by following the instructions to build a specific model or by using your imagination to build something entirely new. Both ways of playing with Legos are valid and exciting in their own way, just like both Boolean algebra and stone spaces are important and powerful tools in mathematics.