ELI5: Explain Like I'm 5

Pointclass

Have you ever played a game where you had to put different types of shapes into different bins? For example, you had a bin for squares, a bin for triangles, and a bin for circles. Pointclass is kind of like that game but with math shapes called sets.

In math, a set is a group of numbers that have something in common. Some sets are really small, like the set of even numbers (2, 4, 6, 8, etc.) and some are really big, like the set of all numbers. Pointclass is a way to organize sets based on how complicated they are.

Just like in the shape game, there are different bins for different types of sets. The easiest bin to put a set in is called Delta-0. This bin holds sets that are really simple and easy to describe using math. For example, the set of even numbers is a Delta-0 set.

But just like in the shape game, some sets are trickier to put in the right bin. There are bins for sets that are really complex and hard to describe using math. These might include sets that have weird patterns or that go on forever in a strange way. These bins are called higher-order pointclasses.

Overall, pointclass is a way for mathematicians to organize and study sets based on how complicated they are.