If you have generated a seed phrase or private key, the wallet you used can give you the option to backup the seed phrase or private key using QR code. You can use the QR code to as backup. So that anytime you want to recover the wallet you can use the QR code backup to recover you wallet as it contains the seed phrase or the private key. But I will not advice you to use this method for backup. It is better you wrote down your seed phrase instead which is better.