2-Step Verification or Out-of-Band
This process is completed by generating a software token on a server and sending it to a user. The token can be sent via:
SMS (Short Message Service): The code is sent to a registered phone number
Email: The code is emailed to a registered email account
Push Notification: The code is sent to an authenticator app running on a smartphone or PC.
Phone call: The code is sent as an automated phone call (voice) to a registered phone number
