Two-factor authentication in iOS 9 and OS X El Capitan: What you need to know

[iMore.com]

The idea behind two-factor authentication in iOS 9 and OS X El Capitan is exactly what the name implies: Your password alone is no longer enough to access your account, you need something else as well. So what happens if something goes wrong and you get locked out? What happens if someone tries to hack their way in?

Full story from the iMore Blog...