This feature is useful when restricting the recording's access to specific email addresses.
When this option is enabled, the recording visitors must either authorize using their Google account or enter an email to which a verification code will be sent. Only the verified emails matching the allowed keywords will be able to view the recording. You can add multiple keywords to the allowed list.
For example, if you want to restrict access to the recording for your company's employees and you know each of your employees has an email with the domain,@acme.com then you can add @acme.com to the allowed keyword.