QR codes are machine-readable code consisting of an array of black and white squares, typically used for storing URLs or other information for reading by the camera on a smartphone.
From the badge editor, select the QR code generator and select the code type either with QR type or Barcode type
After selecting, select the 'Attendee Field' eg: name or registration no. etc and it will be displayed thereafter.
It depends on what field you have selected while generating the QR code
It is always advisable to have a unique field as a QR code or Barcode like a registraton number etc. if you wish to track your attendees.