You can scan a QR-code with the camera of your mobile phones.
Scanning a QR-code works on Android phones from version 9.0 and on iOS from version 11.0. In these versions you can just use the camera function of your phone to scan QR-code, all you have to do is point your camera on the code. After that you will be redirected to a specific webpage. You can also scan QR-codes on older phones but you will need a third-party app for that to work.