ELI5: Explain Like I'm 5

qr code

A QR code is like a secret message written in a square, like a secret code. They're all over the internet, so you might have seen one before without even knowing it. When you take a picture of it with your phone, your phone will read the message inside the code and do what it says. It can be used to open websites, send people money, get discount codes, or even open a door. It's a really smart way to make things easier, and keep them secret.