How Does Two Factor Authentication Work
With two-factor authentication, you are the only one to access your Apple ID account on devices you trust, like your iPhone, iPad, or Mac. When you wanna sign in your account in a new device for the first time, you should provide two pieces of information--the password to your Apple ID and a six-digit verification code that's automatically shown on your trusted devices. You can verify that you trust the new device by entering the code. For instance, you have an iPhone 7, and you want to sign into your account on a newly purchased MacBook Pro for the first time, you will be required to enter your password and the verification code that's automatically displayed on your iPhone 7.
As the password is not enough to access your account, two-factor authentication greatly boost the security of your Apple ID and all the personal information you store with Apple.
Once Apple ID was successfully signed in, you won’t be asked for a verification code on that device again unless you sign out completely, erase the device, or need to change your password for security reasons. When you sign in on the web, you can choose to trust your browser, so you won’t be asked for a verification code the next time you sign in from that computer.
To let you better understand the two-factor authentication, I would like to elaborate some terms as below:
1. What is a trusted device
A trusted device is an iPhone, iPad, iPod touch with iOS 9 and later, or Mac with OS X El Capitan and later that you've already signed in to using two-factor authentication. A trusted device can be used to verify your identity by displaying a verification code from Apple when you sign in on a different device or browser.
2. What is a Trusted Phone Number
A trusted phone number is a number that can be used to receive verification codes by text or phone call. You must verify at least one trusted phone number to enroll in two-factor authentication.
You should also consider verifying other phone numbers, such as your alternative phone number, phone number that used by your family or friend, you can use them in case the first number is not accessed.
3. What is a Verification code
A verification code is a temporary code sent to your trusted device or phone number when you sign in to a new device or browser with your Apple ID. A verification code is different from the device passcode you enter to unlock your iPhone, iPad, or iPod touch.
