One-way compression function

Okay kiddo, imagine you have a bunch of Legos and you want to squash them down into one small toy. A one-way compression function is like a magic machine that can squish those Legos into one toy but you can't turn that toy back into the Legos you started with. It squishes the Legos down so much that they become something completely different and there's no way to know what they originally looked like.

In computer speak, a one-way compression function takes a bunch of information (like letters, numbers, or pictures) and squishes them down into a smaller amount of information. But you can't go back and figure out what the original information was just by looking at the squished-down result. It's a special kind of math that helps keep things safe and secure on the internet.