How to configure Google's two-step authentication

First, let’s clarify what two-step authentication actually means. In Google’s case, it works this way: If you enable two-factor authentication, when you next log in to your Gmail account, you’ll first proceed as you always do—by providing your username and password. But before you get to your inbox, Google will next demand a separate code.

Of course, you won’t know what the code is offhand. Thus, for the second factor of authenticating that you really are who you’re claiming to be, Google will send a text message to your phone containing the six-digit code to use.