Cardboard SDK NFC & External permissions

The Google Cardboard SDK says:

• android.permission.NFC permission is required by the Cardboard SDK to access Cardboard's NFC tag.
• android.permission.READ_EXTERNAL_STORAGE and android.permission.WRITE_EXTERNAL_STORAGE. These permissions are required by the Cardboard SDK to pair the user's phone to their VR viewer.

What does it mean by pair my phone to my cardboard? I don't think cardboard has any ability to be connected since it doesn't have any electronic things on it....

Cardboard SDK NFC & External permissions