A QR code is a 2 dimensional bar code. The QR code on the left is for the Stone u3a website.
Use your smartphone’s built-in camera app (iPhone or Android) to scan — Otherwise download a third-party scanner.
Before scanning, make sure the QR code looks legitimate (Avoid scanning codes in public places that seem tampered with or pasted over official posters)
When scanned, before tapping, preview the website or action Never enter passwords or payment info unless 100% sure of the source.