Google has a new way to secure your account called Google’s two-factor authentication system (2FA). Previously if you want to use this you should have a six-digit code or USB security dongle connected to the system. “Google prompt” is a new way, it will just uses a push notification at the time of sign in. After entering password, you will get a pop up notification in your mobile asking if you want to sign-in and if you press “yes” then you are in.
To setup this in your Gmail account, then go to the “Security” section of your Google Account settings, click on “2-Step Verification”. Then you will see the new option called “Google Prompt.” To make sure your account is more secure and avoid misuse of this feature google recommends a strong pattern or pin to your lock screen. If you are using Google promt you no longer can signin with your phone, Google will automatically disable sign in with your phone.