You’re also likely familiar with two-factor authentication. You access your bank’s ATM with your ATM card and four-digit PIN. That’s two-factor authentication: “something you know” (the PIN) combined with “something you have” (the ATM card).
Two-factor authentication increases security, but decreases convenience. You can’t simply get cash out of the ATM by remembering your PIN; you also need to have your ATM card.
Google’s two-step authentication is similar. Once enabled, you’ll enter your username and password (something you know). That’s one factor. Then, Google will send a 6-digit code to your mobile phone (something you have). You enter this 6-digit code to gain access to the account. That’s two factor, or two-step, authentication.
Read this very useful post by Andy Wolber.
