Ultrafilter

An ultrafilter is something that can be used to make choices about a group of things. It works by taking a bunch of things (like a list of numbers) and then separating them into two different parts. The first part has all of the things that are "good" and the second part has all of the things that are "not good." It can help you to focus on the things that you are interested in while at the same time ignoring the ones that you don't want to use. It's like a filter that helps you to make better decisions.