A QR code (Quick Response code) is a special visual method of data encoding and transferring that is usually used for simple and fast semi-automatic interaction with users' mobile devices. It can contain any text data, including URL links. When the user uses their phone to scan the QR code, the data inside the QR code will be decoded. If it is a link associated with a special application, the user's smartphone will react in a predefined way. For example, it can suggest to the user to follow the URL using a web browser or to send the funds using their crypto wallet application.
An example of a QR code: