Too Long; Didn't Read
Google's Authenticator App Explained and Reviewed by rupesh Rupesh Senior at IIT Bombay. The base idea is pretty simple. Apart from just the password, many websites might be sending you an OTP on the phone to grant access. Many secure websites recommend, even enforce you, to use such two factors. More than often, the possession part is your phone number. This is the idea behind Google Authenticator. It generates a new OTP for you which is a 6–8 digit number that you can type in. This OTP is regenerated in 30 seconds and older OTP expires.