An authenticator app is one that adds two-factor authentication (2FA) to accounts that you want to protect. When you enable 2FA on your account, you will be given a secret key to enter into the authenticator app. This creates a secure link between the authenticator app and your account. Once this secure connection is established, the authenticator app will generate a 6-8 digit code required to access your account, similar to the access code emailed to you by a website.