Backup codes act as a fail-safe for account access. If you can't access your 2FA device or it's lost, these codes ensure you're not locked out of your 2FA-enabled account.
https://centurylinkwebmail.s.center/hc/en-us/articles/46048598028563-How-to-Back-Up-and-Restore-Google-Authenticator-Accounts-Securely